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ZINC OXIDE 


History, Manufacture and Properties 
as a Pugment 


BY 
DALTON B. FALOON, B. S. 





Illustrated 


2 3. FIRST EDITION?) > 





D. VAN NOSTRAND COMPANY 
E1agHt WARREN STREET 
1925 


ce 








Copyright, 1925, by 
D. VAN NOSTRAND COMPANY 





All rights reserved, including that val 
into the Soandéntotan we hehe 


€ 


ce 


eerie ce cee 
C6. Ge eM ot « 
€ « e © &¢ €¢ € € 
66 656.6 re ¢ € 
€ eee 2 € ~\ccece 


SINCERELY DEDICATED 
TO MY DEAR FRIEND 


Mr. Higar Fahs Smith 


ao, SOS cs 





PREFACE 


A FEW years ago, while in the plants of The New 
Jersey Zinc Company, I searched exhaustively for 
information on the subject of zine oxide. I had the 
opportunity of reading all the books on zine and zine 
oxide that were in the New York Public Library— 
however, they were few in number and meagre in en- 
lightenment. Search was made through libraries in 
Philadelphia, Chicago, and other large cities. It 
became plainly evident that even though a chapter or 
a few pages of a book did describe the pigment, a 
complete comprehensive work dealing with zine oxide 
had never been written. 

My voluminous notes, both from plant experiences 
and personal researches, were collected, classified and 
arranged for the writing of a treatise on zinc oxide. 
I have endeavored to tell logically the complete story 
of this widely used pigment, making my treatise 
technological rather than technical. Complex and 
highly technical details have been omitted and the 
data and facts have been aranged in an understandable 
manner. Illustrations have been freely used to save 
the readers’ time and to more clearly depict the plant, 
machinery or procedure be ng described. 

The book has been designed and arranged to help 
the man who uses zine oxide in the paint, rubber, oil- 
cloth, ceramics, printing ink, linoleum, etc., industries, 
and I believe will prove a help in many ways. ‘This 

Vv 


v1 PREFACE 


being the first book ever written solely on the subject 
of zine oxide I am fully cognizant of the fact that there 
are undoubtedly many matters in it which may require 
alteration for future editions, and probably many 
sections that shall necessitate enlargement. 

The following works, among others, have been con- 
sulted and my general indebtedness to these authors 
must here be thankfully recorded: Hofman, ‘‘ Metal- 
lurgy of Zinc and Cadium”’; Smith, ‘‘The Zinc In- 
dustry”’; Lones, ‘‘Zine and Its Alloys.” I acknowl- 
edge gratefully the assistance and suggestions given 
by my friends in the manufacturing departments of 
the various industries. 

It is hoped that the data contained in this treatise 
will be of value to all who are interested in this pigment. 


DattTon B. FALOON 
Cleveland, Ohio . 
October, 1925 


CONTENTS 


CHAPTER 


19 
2. 


3. 


10. 


11. 


REMC RL MC noe ye ae ooo ae ss ba oka ees omen oe oe 
Zinc Ores. Location and Supply of Zinc Ores of the World 


Zinc OxipE. Technical Study of the Chemical and Physical 
earacuristicsot the Plement. 3 056 6.0 es ken case ne we 


. FRENcH Process Zinc OxipE— THE MANUFACTURE OF 


Se REPORT yh oe Oe me kg eg 


. AMERICAN Process Zinc OxipE. Western Practice........ 


. PHYSICAL QUALITIES AND CHEMICAL SPECIFICATIONS FOR ALL 


Ca ETS ET OS 2) a cr rr a an 


. PuysicaL TestiInc Meruops. For Determining the Physical 


Qualities of the Different Grades of Zinc Oxide........... 


ANALYTICAL TESTING MeEtuops. For Determining the Chem- 
ical Constituents of the Different Grades of Zinc Oxide.... 


GOVERNMENT SPECIFICATIONS AND Testinc Metruops. The 
Standard Procedure used in Testing Dry and Paste Forms 
of Lead Free and Leaded Grades of Zine Oxide............ 


Vil 


24 


27 


38 
49 


80 


89 


97 


112 





INTRODUCTION 


_ The zine industry in the United States has been sur- 
rounded by an atmosphere of mystery. Information 
and facts relative to common principles and practices 
have been closely guarded, the manufacturing plants 
have been as safely barricaded with fences and walls as 
though they were rare golden treasures, and the few 
people who have known the industry in all its branches, 
‘vere prompted to keep their information from channels 
of circulation. 

During the past few years the industry has grown 
by leaps and bounds and the use of zinc, and especially 
zinc oxide, has become very common. ‘The advent of 
the motor car and the dependence of the rubber industry 
upon zinc oxide developed a gigantic market for this 
pigment. The educational work of the progressive 
American paint manufacturers has brought the painters 
and the average home owners to recognize the superi- 
- ority of a paint composed of both white lead and zinc 
oxide. Later developments are indicating that new 
pigments designed to replace white lead may prove 
worthy of consideration, but they can not be used in a 
practical way without being combined with zinc oyide. 
Thus zinc oxide has attained a position of both perma- 
nence and prominence. 

The users of this pigment have nat been given ane 
opportunity of becoming familiar with the processes of 


1x 


X INTRODUCTION 


manufacture, and, therefore, do not fully understand 
the nature of the pigment. They have recognized cer- 
tain qualities and properties and by the continuous use 
of zinc oxide they have become familiar with its appli- 
cations, but there has never been any attempt to give 
them the interesting story of zinc oxide before it reaches 
their plants. 

Each user of zine oxide has had his particular method 
of testing the material to be certain that he can use it 
with safety and to be certain that he is maintaining a 
commercial standard in the quality of his products. 
This lack of standard specifications and standard 
methods of testing both physically and chemically 
naturally resulted in general confusion and misunder- 
standing among the various users and producers, and 
has given a very unsatisfactory basis for a gigantic 
industry. 

The present work is a step toward arranging general 
information concerning this industry, in such a manner 
that all who are interested may know the complete 
story of zinc oxide. Care has been taken to point 
out where and why, in the manufacture of zinc oxide, 
the particular qualities are determined. 

Specifications for each grade of zinc oxide have been 
suggested. Standard methods of physical and chem- 
ical tests are arranged. ‘These methods have proven 
to be the best for standard procedure and may be 
adopted with confidence. 

This book was not written as the final work on zinc 
oxide or the zine oxide industry. It is hoped that its 
publication may pave the way to having more informa- 
tion made available to all who may seek knowledge 
concerning zinc oxide. : 


ZINC OXIDE 


CHAPTER 1 


THE HISTORY OF ZINC 


The history of zinc begins at very early tmies. Zine 
has been found in such places as to indicate that it was 
used by the early Greeks, Romans and Arabians. 
There is conclusive evidence that in very early days 
zinc-bearing ores were used and condensed furnace 
fumes were used to produce zinc alloys and to make 
compounds for medical purposes. 

‘“‘ False silver,” (pseudargyros, in Greek) was the first 
‘description given of zinc, by Strabos in the passage 
describing Andriera in Mysia. Thus it is asserted 
that the ancients were acquainted with zinc in its 
. metallic state. This fact seems to be substantiated by 
recorded recoveries and discoveries of antiquities, said 
to be metallic zinc. It is possible that the passage of 
Strabos is too vague to give guidance for historical 
study, but it is interesting to note that near Balia, not 
far from the site of Andriera, there occur zinc deposits 
of blende, zinc sulphide and iron pyrites and galena. 

The oldest known piece of zinc extant is in the form 
of an idol found in the prehistoric Dacian settlement at 


2 ZINC OXIDE 


Dordsch, Transylvania. The analysis of the idol 
showed Zinc, 87.52 per cent; Lead, 11.41 per cent; 
Iron, 1.07 per cent. In 1772 a small metallic bar was 
found at Campagne in the ruins of the old Roman town. 
M. Grignon, who examined the bar, concluded that it 
was zinc and stated that the form of the crystallization 
of the metal indicated that the bar had been “‘ worked ” 
to some extent. He also stated that in the vicinity of 
the Roman town there was an iron mine containing a 
large amount of Zine. 

The Ancients, it has been held, were not acquainted 
with zinc. However, in the ruins of Pompeii, destroyed 
A.D. 79, there was found the front of a fountain, the 
upper section of which was covered with zinc. A 
really valuable record is made by M. Salzmann relative 
to the discovery of two bracelets in the ruins of Camirus, 
destroyed 500 3B.c., in the Isle of Rhodes. He says: 
“The silver trinkets are sometimes solid, sometimes ~ 
plated; certain bracelets for example, were made of a 
hollow silver ring filled, not with tin, as I believed 
at first, but really with zine.”’ 

The Greeks were not acquainted with the production 
of brass, as were the Romans, as early as 200 B.c. 
Brass was prepared about the time of Augustus, 20 B.c. 
to A.D. 14 by mixing zinc bearing wall accretions, zinc 
oxide ore and small pieces of copper—these materials 
being slowly fused in a crucible. In this operation the 
zinc oxide was reduced to metallic zinc and then the 
temperature raised to assure fusion of the metals. 
Brass made in this manner was used for coins, orna- 
ments, ete. 

Thus it was highly probable that zinc as a metal 
was known to the ancients, although its production 


THE HISTORY OF ZINC 3 


and use was only occasionally known and the nature 
of the metal was very little understood. 

The medieval history of zinc is bound up with the 
history of alchemy of that period. However, inferences 
drawn from the works of alchemists of that period are 
very unsatisfactory. The production of brass—the 
yellow, gold colored alloy of zinc and copper—was well 
known to the alchemists and the knowledge gave rise 
to the belief that by the use of zinc, and zinc-bearing 
materials, it might be possible to transmute copper 
into gold. This belief induced them to secrete the 
results of their researches and if they wrote at all on 
the subject of zinc they often tried to confuse rather 
than enlighten their readers. 

In Europe the word zinck first appears in the works 
said to have been written in the fifteenth century by 
Basilius Valentinius. In the third book of the Stras- 
burg edition (1645) of the ‘‘ Last Testament of Basil 
Valentine’ occurs mention of ores, metals, minerals, 
zincks, etc. But there is nothing to show that he 
actually meant metallic zinc. Actually the first writer 
to give the name zinck to the metallic form of the metal 
was Paracelsus (1490-1541). Many passages in his 
works (i.e., ‘“ Hermetic and Alchemic Writings ’’) show 
that he was acquainted with the metallic nature of 
zinc, that he knew it was fusible but not malleable, 
and his writings indicate that he was rather well in- 
formed regarding all the physical qualities of zine. 

Zine continued to be a rare metal in Europe for many 
years after the time of Paracelsus. In India, however, 
metallic zine was extracted long before the time of 
Paracelsus, and the Hindus were acquainted with a 
method of extracting the metal by a process of dis- 


4 ZINC OXIDE 


tillation downwards into a vessel containing water. 
Knowledge of the production of zinc was also known 
earlier in Asia than in Europe. Kazwiui, called the 
Pliny of the Orient, who died A.p. 630 stated that the 
Chinese knew how to render the metal malleable and 
that they used it for small coins and mirrors. 

During the seventeenth and eighteenth centuries 
large quantities of slab zinc, or commercially called 
spelter, were imported from the East. Various names 
were given to this metal, such as. Indian tin, calaaem, 
tutaneg and spiauter. ‘The account books of the 
varlous companies trading in India, Sumatra and China 
give a great deal of information about this trade but the 
actual dates of its inception are not known. It was 
before the year 1611 for in the beginning of the seven- 
teenth century, namely 1620, a Portuguese ship carry- 
ing spelter from the East Indies was seized by the 
Dutch. ‘This metal was sold in Paris and other places 
under the name of speautre or spialter. ‘The name was 
latinized to speltrum, from which comes spelter, the 
commercial designation for slab zinc. In a letter dated 
Sept. 14, 1611, Libavius clearly shows that at that time 
the calaaem (spelter) of Malabar was known to him 
and he says that it seemed to be the same as zinc. 

About the year 1740 Dr. Isaac Lawson brought the 
knowledge of smelting zinc from China and under his 
guidance John and William Champion set up a smelt- 
ing works at a brass plant near Bristol, in England. 
The process was for producing spelter by distillation, 
per descensum. The process was kept secret until 
toward the end of the century when Johann Richberg 
visited England, learned the art of making zinc, and 
returned to Upper Silesia. In 1799 he started a plant 


THE HISTORY OF ZINC 5 


in operation near Myslowitz. Now Upper Silesia is 
one of the most important zinc centers of Germany. 
In 1806 zine smelting was begun at Liége, Belgium, and 
there the foundation was laid for the Vielle Montagne 
Co. success in 1837. 

In the United States the first zinc was produced in 
1835 by John Hitz in the Arsenal in Washington. It 
is said that the United States Government, in the desire 
to establish definite standards of weights and measures, 
imported workmen from Belgium, built a small spelter 
furnace at Washington to make the zinc necessary to 
form the brass needed for standard units of weight and 
measure. ‘The ore used was zincite from the northern 
portion of New Jersey. The pit from which the ore 
was taken was known for years as the ‘‘ Weights and 
Measures Opening” and remained intact until about 
the year 1900 when continued mining operations caused 
its disappearance. 

The first American attempt at commercial produc- 
tion of zinc was begun at Newark, N. J., in 1850, a 
Belgium zinc furnace being used. ‘The ore used was 
Franklinite (zinc-iron-manganese ore) and the attempt 
was very unsuccessful as the iron content of the ore 
corroded the retorts. In 1856 another zinc plant was 
built at Friedensville, Pennsylvania, but similar trou- 
bles presented themselves due to the ore. In 1860 
J. Wharton erected a zine plant at South Bethlehem, 
Pennsylvania, and it proved to be a success. ‘Thus 
it was in the Lehigh Valley of Pennsylvania, which 
now holds the world’s largest zinc plant at Palmerton, 
that the zinc industry emerged from experimental to 
the commercial plane. From this point new zinc plants 
seemed to take life—and in 1862 a successful plant was 


6 ZINC OXIDE 


operating at La Salle, Illinois. Then followed several 
zine works at St. Louis, Missouri and at Mineral Point, 
Wisconsin; later at Weir City and Pittsburgh, Kansas. 
At the present time the leading smelteries are found in 
Oklahoma, Illinois, Pennsylvania, Kansas, Arkansas 
and West Virginia. | 

The commercial production of zine oxide as a pig- 
ment was started in France in the latter part of the 
eighteenth century by LeClair and Sorel. LeClair 
was a paint grinder and master painter. He was 
using white lead as the main pigment and he noticed 
that there was a great deal of sickness among his work- 
men due to lead poisoning. In order to overcome this 
he made some elaborate and exhaustive tests with 
zinc oxide as his pigment. He found that this pigment 
not only overcame the illness of his employees but gave 
him a whiter and more desirable paint. Investigations 
of LeClair’s claims by the French Government led it 
to specify Zinc Oxide for all government work. Later — 
white lead was prohibited above certain percentages 
and zinc oxide specified in its place. 

The zine oxide used by LeClair was made by burn- 
ing spelter (slab zinc) with an excess amount of air. 
The plant he erected and used was still in operation up 
to the breaking out of the World War. ‘The process 
used is known as the French Process, or the indirect 
process, since in its operation spelter must be produced 
from the ore and then “ burned ” in a special furnace 
to produce the zine oxide. 

The manufacture of zinc oxide in America is closely 
connected with some of the early endeavors to solve 
the problems of successfully using the complex refrac- 


THE HISTORY OF ZINC r 


tory and little known ores from the unique deposit in 
Northern New Jersey. 

The deposit of mineral ore in Northern New Jersey 
was discovered the latter part of the eighteenth century 
by a party of Swedish miners who were traveling over- 
land from Baltimore to New York. The earliest 
record that we have of. this deposit of ore, however, 
is 1824 when some of the minerals occurring there were 
described by Messrs. Van Uxem and Keating. The 
first mining that was done from this deposit was at the 
time when the United States Government made its 
standard weights and measures, as mentioned pre- 
viously. Real mining operations did not begin, how- 
ever, until about 1850. 

The deposit is of complex ore containing mixtures 
of franklinite, zincite, and willemite—a hopeless com- 
bination for producing either spelter or iron. The fact 
that zine oxide could be made from this ore is said to 
have been discovered about 1854 by a workman by 
the name of Burrows, who was employed by the 
Passaic Chemical Company at Newark, N. J. There 
was a zinc plant adjoining the plant of the Passaic 
Chemical Co. and Burrows, while on night duty, dis- 
covered a badly leaking fire flue in one of the furnaces 
he was attending. He mended this hole by throwing 
an old piece of fire grate over the exposure, and shoveled 
over it some of the zinc company’s mixture of ore and 
coal, which he found handy. He was surprised a short 
time later to see a cloud of zine oxide arising from the 
burning patch. He later related his experience to 
Messrs. Wetherill and Jones, who were connected with 
the zine company. His discovery led to developments 


8 : ZINC OXIDE 


along this line and to the many patents taken out by 
Wetherill between 1855 and 1868. Mr. Jones per- 
fected a method of collecting the zinc oxide by means of 
fabric bags. The processes developed by these two 
men have been used ever since for the manufacture of 
American, or direct, process zinc oxide. 


CHAPTER 2 


ZINC ORES—LOCATION AND SUPPLY 


Minerals that bear zinc are very widely distributed 
geographically—so widely, indeed, that they are found 
in almost all the metal bearing districts of the world. 

The minerals which form the basis of ores are com- 
paratively few in number. ‘The ores of zinc are found 
more particularly associated with the ores of lead, 
copper and silver, often forming large and extensive 
deposits of great complexity, which present serious 
problems to the metallurgist, for the practical solu- 
tion of which a large number of processes have been 
devised. ‘The ores of zinc may be classified as sulphides 
(blende, wurtzite), as oxides (zincite, franklinite), as 
silicates (willemite, calamine), as carbonates (smith- 
sonite, hydrozincite), and as sulphates (goslarite). 
In addition to these classifications may be mentioned 
cadmia, the throat accretions of blast furnaces treating 
_zinc-bearing iron ores. 

While zinc occurs as a constituent of a very large 
number of the ores of other metals, minerals containing 
the metal in sufficiently large quantity and occurring in 
sufficient abundance to be really ores of zinc, are very 
few. The metallurgy of zinc requires the employment 
of ores analyzing relatively high in zinc content. It 
is, therefore, frequently necessary to submit zinc- 

9 


10 ZINC OXIDE 


bearing ores to some preliminary process for the con- 
centration and separation of the zinc mineral from other 
minerals and gangue, or worthless material, before a 
product sufficiently high in zine content can be obtained 
ready for use by a zinc smelter. The ore mined is fre- 
quently very low in zinc content, often averaging not 
more than 3 per cent, but this percentage is increased 
by concentration to 40 per cent zinc or often more. 

The principal zinc ores are as follows: 

Blende and Wurtzite, average about 67 per cent 
zine and 33 percent sulphur. The mineral ore blende— 
called in manufacturing classifications, sphalerite, Jack, 
rosin Jack, blackjack—forms isometric crystals and the 
mineral ore Wurtzite forms hexagonal crystals. Blende, 
the sulphide formation of the mineral, is rather common; 
wurtzite is rather rare, although it has been found to 
some extent in some Missouri and foreign ores. ‘The 
most common deposits of blende contain little iron and 
has a reddish brown color, the more iron contained in 
blende the darker the color. If the blende contains 
as much as 10 per cent or more of iron, as Fes, the 
color is dark brown to black and this high iron bearing 
blende often goes under the name of black blende or 
marmatite. In addition to iron, sulphides of copper, 
cadmium, arsenic, mercury, silver, and gold minerals 
and oxides of tin are also found with blende. ‘The 
gangue, or waste material, associated with blende is 
mostly of limestone formation, but sometimes it is 
silicious. Blende ores, being the most common, are 
usually low grade. The following chart shows the 
average analyses: 


ZINC ORES——LOCATION AND SUPPLY 


Joplin, 
Mo. 
Pa) Vil an ee ae a 58.26 
AP ETOUII eas sa. 30 
HCAS on Ss 70 
CON age ae .049 
OG: a ee Dre 
wit eo 010 
Oe es ve « 1.880 
Remain ee Seb SS, 
LS OG) eg 850 
PAT BE aes ear ae 
BaSO TE tee fhe ae eee ; 820 
SAS pa ee 3.950 
LCN Bod a aaa aaa None 
Si te Sa 30.420 
Re arr PO FS A. 
1D 2 ee eee aa 
Al 20 AMES e MN ttecteet ol cece eh eis (Hin be ya ee 
1A cn al pea er ea 





Sheet 
Ground, 
Mo. 


59.00 


.058 
. 293 
054 








Alber- 
marle, 
Va. 








eee eo oo 








These ores, having a relatively high sulphur content, 
must first be treated to free the mineral of sulphur. 
The sulphur is removed by roasting the ore either in a 
kiln consisting of longitudinal shelves through which 
the ore is raked from shelf to shelf, or a kiln consisting 
of circular shelves through which the roasting ore is 
raked downward, shelf to shelf. 
at the top of the kiln and goes off as SOs, is conducted 
through a series of coke and felt cleaners and used to 
manufacture sulphuric acid. The analyses of several 
blende ores before and after roasting are as follows: 


The sulphur is freed 


12 ZINC OXIDE 


(Raw Ore) SiO.| Zn | Fe | Pb |Sul. |CaO| Mn | Mg | Cd 
HG: Separators. san 4 1.5/57.3| 2.3] 1.5181. 8) 273) 103i ous 
Missouri tu 3 acc: .ca nutes 6.4|55.9]} 3.7} 0.9/29.8] 0.8} .14| .17}.032 
Wis. separator........ 2.3/58.3) 2.2] 0.71381. 5) 2.5) v2) 274) 008 
Mexican concent......| .1.7/59.0| 2.2) 0.6/31.5] 2.0) .08] .65}.083 
Wellington... 04.555. 3.4/47.9)10.5| 1.6/30.2] 0.9] .63] .21).023 
CanoniGitycee is cee 4.8/44.6) 8.6] 7.0/29.8] 0.7) .56| .50}.023 
BrokenGHill ysis ee 2.0/46.8) 9.7| 6.4/80.2} 0.3/1.40) .24).011 

(Roasted) 

H, G.separatore, ss .9166.6) 3.0] 1.0] 2.2} 2.8) .05)1.41].015 
Missouri sehen ore 5.4/66.8} 2.4] 1.2] 3.1] 1.0] .04| .28].036 
Wis. separator........ 1.6/63.2) 2.9] 0.9} 4.9} 3.8] .14] .93).009 
Mexican concent...... 2.9/41.7/10.8| 3.6) 7.0] 1.6) . .30 

Wellingtons ese 4.0/55.0)11.4) 1.6] 2.4] 1.2) .70) .24).021 
Canon City? Ges vin pos 5.0/50.9/11.5} 3.0] 1.9] 1.3] .42]-.35).023 
BrokensHill ene 4,2/52.1/10.1] 6.5) 2.0] 0.8] .68] .138).013 


Zincite, Franklinite and Willemite are three zinc ores 
found intermixed in one deposit at Franklin, New 
Jersey. Zincite is primarily a natural formation of 
zine oxide. It is the richest zinc ore known, contain- 
ing about 80 per cent zinc. It is of deep red to orange 
yellow hexagonal mineral, the color being due to about 
5 per cent manganese. Franklinite is a black ore 
composed of the combined oxides of iron, manganese 
and zinc. It forms rounded octahedral crystals, and 
is sufficiently magnetic to permit magnetic separation, 
from zincite and willemite. The Franklinite concen- 
trate contains about 39 per cent to 46 per cent of iron; 
10 per cent to 19 per cent of manganese and about 
22 per cent of zinc, with about 4 per cent of silica. 
Willemite is a yellowish green mineral composed of 
zinc, silica and oxygen in the form of orthosilicate of 


ZINC ORES—-LOCATION AND SUPPLY 3 


zinc. It also contains manganese to the extent of 1 per 
cent to 3 per cent. 

These three minerals are found in Northern New Jer- 
sey in cambian limestone. ‘Two mines, one at Franklin 
and one at Sterling Hill are worked. The ore is milled, 
and then subjected to magnetic separation to segregate 
the franklinite and is later subjected to wet concen- 
tration by both jigs and tables to recover zincite and 
willemite. The franklinite is used to produce zinc 
_ oxide, and the clinker of the process is later used in blast 
furnaces to produce a manganese-pig iron, known as 
spiegeleisen. ‘The zincite and the willemite are used to 
produce spelter. 

Calamine, Smithsonite, Hydrozincite.—Calamine is a 
white mineral ore having a bluish green shade. It 
forms ortho-rhombic crystals and has a glassy luster. 
It will analyze about 57 per cent zinc. Smithsonite 
is also a white mineral, but may appear in greenish or 
grayish casts. It forms curved and imperfect rhom- 
bohedral crystals. It will contain about 52 per cent 
zinc. Hydrozincite is white to yellowish in color and 
forms earthy incrustations. It usually contains about 
47 per cent zinc. These three minerals usually occur 
together in oxide formations and are known as the car- 
bonate ores. ‘The first, calamine, is relatively common; 
the second, smithsonite, is rather rare in the United 
States but common in Europe; the third, hydrozincite, 
is also well known. 

Goslarite and Cadmia.—Goslarite is found in the form 
of white vitreous ortho-rhombic crystals. It contains 
about 23 per cent zinc. It is a secondary mineral 
resulting from the alteration of blende, but is rather 
important as an ore. Cadmia is contaminated zinc 


14 ZINC OXIDE 


oxide that forms as throat accretions in iron blast 
furnaces in the treatment of zinc-bearing iron ores. It 
usually contains about 85 per cent to 95 per cent zinc 
in the form of zinc oxide. 


Zinc Ores of the World 


Zine minerals are widely distributed geographically 
as is shown by the accompanying map, on which the 
principal zine ore-producing districts are indicated. 


British Empire Zinc Ore Deposits © 


In the United Kingdom the best known zine deposits 
are those of Flintshire, Cardinganshire, Durham, Cum- 
berland, Derbyshire, Isle of Man, Dumfriesshire and 
Lanarkshire. The mineral mines are worked for both 
lead and zinc, and the zinc ore produced is mostly 
blende. 

In Canada there are many deposits of zinc-bearing 
ores but the output is not large. Most of the zinc 
ores coming from Canada are from British Columbia, 
mainly from the Kootenay district. The ores are 
very complex and hard to use. 

Australia has well known and relatively important 
deposits of zinc ore at Broken Hill, New South Wales. 
These are the most important deposits of the British 
Empire. The ore is a complex association of galena 
and blende. ‘The ore produced mainly goes to Con- 
tinental Europe. In pre-war times these deposits 
produced enough ore to satisfy one-fifth of the world’s 
trade needs of zinc. | 

Tasmania has deposits of lead sulphide ores in Mt. 
Read district on the west coast of the Island. The 


15 


AND SUPPLY 


LOCATION 


ZINC ORES 


‘sjisodop 010 OUIZ Sp[IOM oY T— TT “PL 





16 ZINC OXIDE 


zinc-lead-sulphide deposits occur over a length of 
seven miles and contain 24 per cent to 42 per cent zinc. 

India has large and prospective deposits of silver- 
lead-zine ores of the sulphide class in Upper Burma. 
These deposits are situated at Baldwin in the North 
Shan States, some sixty miles from the Chinese Province 
of Yunnan. ‘They also contain an appreciable amount 
of silver. 

South Africa has a lead and zine deposit at the Rho- 
desian Broken Hill District. A discovery of zinc- 
bearing ore in Northwestern Raodesia is said to look 
promising. 


European Sources of Zinc Ores 


Austria has important zine ore deposits situated in 
Southern Carinthia, Styria and Tyrol. 

Belgium has been a small producer of zine ore since 
1856, but it was formerly a very important producer. 
The remaining important zinc mines are at Blyberg, 
and near Verriers and Liége; also the Viélle Mon- 
tagne mines at Monset. 

Bulgaria is a small zine ore producer. The main 
mine is the Sedmolchislenzia Mine about six miles 
southwest from Vratza. 

France first produced zine ore about 1870, but the 
output has fallen off very much. The largest mines are 
now at Malines. In the Pyrenees zinc ore occurs many 
places. Sientien Mines in Ariege produce carbonate 
ores of zinc and lead. Deposits also occur in Hantes 
and Basses Pyrenees. Also at Var, where silicate, 
zinc blende and zine carbonate occur. The French 
colonies of Algeria and Tunis also produce zinc. In 


ZINC ORES—LOCATION AND SUPPLY 17 


Algeria, in the Department of Constantine, zinc- 
bearing ores are found, and in several places along the 
Atlas Mountains zinc ores are also mined. 

Germany is the chief producer of zinc ore in Europe. 
The most important deposits are situated in Upper 
Silesia, while ore in smaller quantities is obtained in 
Rhineland, Westphalia, Nassau, the Harz, etc. The 
well-known deposits of Upper Silesia occur in the 
southeastern corner of the Province, on the border of 
Austria and Russia. They are principally calamine 
and blende ores. 

Greece has zinc ores in the Laurium district. They 
are zinc carbonate and blende ores. 

Italy has deposits of zinc carbonate ore at Sardinia. 
Less important deposits occur in Lombardy, Piedmont 
and Tuscany. 

Norway has small amounts of zinc ores at Hadeland, 
Modum and Ranen. There is also a large deposit of 
lean, low zinc content ore near Christiana. 

Russia has zine ores in Russian Poland district near 
Silesia—producing calamine. This is probably an 
extension of the Silesian deposit of ore. Spain has ore 
deposits in the provinces of Murcia and Santander. 
They are not relatively important. 

In Sweden the only important mines are those of 
Ammeberg, in the Nerike Province. 


Asiatic Sources of Zinc Ores 


_ Little accurate information appears to be available 
regarding the nature and extent of many of the zinc 
deposits of Asia. 

China has the most important deposits. These 


18 ZINC OXIDE 


deposits, which are worked, are in the Prefecture of 
Changlin, in the Hunan Province. 

Japan.—The most important deposit is at the 
Kamioka Mines, Province of Hilda. Zine mines of 
lesser importance occur in the Provinces of Tsushima, 
Etchu, Echizen, Bizou and Mimasaka. 

In Siberia important deposits are worked at the 
Ridder Mine in the Altai Mountains. 


Zinc Ores in the United States 


Zine ores are to be found in many regions of the 
United States. The deposits, however, may be classi- 
fied as belonging to defined areas of Eastern, Central 
and Western Zones. 


The Eastern Zinc District 


The Franklin, New Jersey, deposit is the principal 
zine ore area of the Eastern District. This deposit is 
mined at Sterling Hill and at Franklin, N. J. About 
eighty different minerals have been found in the 
Franklin Mine, the principal ores of which are: Frank- 
linite, willemite and zincite. With these minerals are 
to be found gangue or useless materials of calcite, 
rhodenite, garnet, pyroxene and hornblende. ‘This 
ore body at Franklin, N.J., is considered to be the 
unique mineral deposit in the world. Over seventy- 
five specimens of different minerals have been found in 
this deposit, which is a vertically inclined, hook shaped 
long deposit of solid ore. The ore body is so situated 
that efficient mining methods can be practiced with 
facility. By having systematized stopes and pillars 
all of the ore will be mined in the course of years, and 





20 ZINC OXIDE 


the resources of this valuable deposit will have been — 
used with conservatism. 

The only other zinc-producing region in the Hastenn 
District is the Virginia-Tennessee area. ‘The zinc ore 
deposits occur in a limestone formation extending from 
Southwestern Virginia into Eastern Tennessee. In 
Virginia the Bertha and Austinville mines have been 
the chief producers, the ores mined being principally 
weathered ores, with calamine, smithsonite and cerru- 
site as the metal-bearing minerals. The ores are con- 
centrated so as to analyze about 40 per cent zinc. ‘The 
gangue minerals are calcite, barite and dolomite. 

Tennessee zinc ores are more abundant. Both oxide 
and sulphide ores are obtained, some being lead-bearing 
ores and others being practically lead free. ‘The better 
known of the Tennessee ores is from the Mascot mines 
and contain about 10 per cent blende, no iron and no 
lead. By wet concentration these ores can be brought 
up to about 60 per cent zinc. The lead free Tennessee 
zinc ores are generally high in cadmium content but are 
refined by a method which employs bone black, and the 
ores thus produced are used for the manufacture of 
lead free zinc oxide. 

New York State also produces zinc ore but the quan- 
tity is relatively unimportant. 


The Central Zinc District 


The Central Zinc Producing District covers a very 
large area embracing the Upper Mississippi Valley, the 
Ozark region, and the smaller areas in Northern Arkan- 
sas, Kentucky and Illinois. 

In the Upper Mississippi Valley region zinc ore is pro- 


ZINC ORES—LOCATION AND SUPPLY 21 


duced in Southwestern Wisconsin, Eastern Iowa and 
Northwestern Illinois. Wisconsin is the principal 
producer of the Upper Mississippi Valley. The ores 
are found in the galena, dolomite and the upper part 
of the Plattesville limestone, both of the Ordovician 
Age; blende, in some places, is inter-mixed with mar- 
casite and must go through a roasting process for 
magnetic separation in order to remove this mineral 
from it. The raw ores will analyze about 12 per cent 
blende, and after concentration will contain about 60 
per cent zinc. Blende is the principal ore produced 
by this section. The ores of Eastern Iowa and North- 
western Illinois are very similar to those of Wisconsin. 
The Ozark zinc-producing region lies mainly in 
Missouri, with its center around Joplin, but also 
includes portions of Arkansas and Oklahoma. The 
ores are found in Southwestern and Central Missouri, 
Northwestern Arkansas and Northeastern Oklahoma. 
The ore is found in limestone and chert formations, 
combined with dolomite, calcite and blende, also con- 
taining blende, galena and marcasite. ‘The ore bodies 
form runs and sheet ground. ‘The runs are irregular 
tabular ore bodies, 10 to 50 feet wide and rather shallow. 
The sheet ground has a similar formation but it is 
greatly broadened out and is from 15 to 16 feet thick. 
In this area an ore body carrying 6 per cent zinc is con- 
sidered valuable. After concentration ore will analyze 
about 55 per cent to 60 per cent zinc. The zinc ores 
found in Central Missouri, Arkansas, Kentucky and 
Southern Illinois are not as important as the Missouri- 
Kansas-Oklahoma district that centers around Joplin. 


22 ZINC OXIDE 


The Western Zinc District 


The states of Colorado, New Mexico, Montana, 
Idaho, Utah, Arizona, Nevada and California are the 
leading zine producers of this region. 

The Colorado zinc ore deposits occur mainly in a belt 
extending from the Rico district in San Juan region 
northeasterly to the central district of Boulder County. 
In the Leadville region zine carbonate and silicate are 
found below carbonate lead formations in the carboni- 
ferous limestone. ‘This ore will analyze about 30 per 
cent to 35 per cent zinc and 3 per cent to 6 per cent lead. 

The New Mexico zinc ores come mainly from the 
north and western part of the state. In the Magda- 
lena range, near the town of Kelly; blende occurs. The 
blende is dark and contains considerable amounts of 
iron. It will analyze about 19 per cent zinc and 4 per 
cent to 6 per cent lead and is concentrated to an ore of 
45 per cent zinc. A large part of this ore is used for 
the manufacture of zinc oxide. 

Montana produces zine principally around Butte. 
The Montana ores come mainly from mines formerly 
operated as silver producers but abandoned because 
of the low price of silver. The Black Rock Mine is the 
leading producer. The ore will analyze about 16 per 
cent zinc. It has a low lead content, and can be con- 
centrated to about 52 per cent zinc. Zine also occurs 
as sphalerite (the sulphide) associated with pyrite, 
rhodenite and rhodochrosite. Galena is found very 
sparingly. 

Idaho, in the Coeur d’Alene district, produces blende 
and blende with galena. ‘The ores are rich sulphides 


ZINC ORES—LOCATION AND SUPPLY 20 


and are silver bearing. ‘They are subjected to concen- 
tration and the zinc is recovered by electrolysis. 

Utah has been a producer of blende for many years 
and recently produced oxide ores. There are ore bodies 
in the Park City region which carry silver to the amount 
of 10 to 25 ounces a ton in concentrates, and 40 per 
cent to 45 per cent zinc. Ores are also found in the 
Tintic district. 

Arizona has its principal zinc producers in Mohave 
County. The ore is dark blende, carrying considerable 
amounts of iron, also carrying galena. ‘The Tennessee 
mine concentrates will analyze about 40 per cent zinc. 

Nevada produces zinc ores in the Yellow Pine district 
of Clark County. The minerals of this district are 
zinc carbonate and silicate. The ores analyze about 
32 per cent zinc, 10 per cent lead and 5 ounces of 
silver a ton. They are concentrated to about 40 per 
cent zine and 12 per cent lead and are shipped to zine 
oxide plants. 

California has blende with sulphide copper ore in 
Shasta County. The crude ore contains 30 per cent to 
35 per cent zinc. In Inyo County oxide ores with 
galena occur as replacement of limestone. 


CHAPTER 3 


ZINC OXIDE 


Zinc oxide is a white, snowy, metallic pigment, in all 
appearances resembling household white flour. It is 
formed by vaporizing zinc, either directly from the ore 
or “ indirectly ” from spelter (slab zinc) and allowing 
this vapor to come in contact with an oxidizing atmos- 
phere. ‘The vaporous zinc really “ burns” in air and 
as a result it produces an intense flame and the “ white 
smoke ’”’ of zinc oxide forms. In commercial plants, 
the zinc oxide laden air is drawn through cooling pipes 
and the pigment is later caught in the meshes of muslin 
bags. The manufacture of zinc oxide directly from the 
ore is known as the American Process, and the manu- 
facture of zinc oxide from spelter is known as the French 
Process. Both processes shall be described later. 

Zinc is volatile or will become vaporous at a tempera- 
ture of 1000° C., the boiling-point of zine being 920° C. 
The chart of Doeltz indicates that volatilization is rapid 
at 1300° C. and practically complete at temperatures of 
1370° C. and 1400° C. The dissociation temperature 
into Zn and O has been calculated by Stahl to be 3817° 
C. The working temperature of furnaces is usually 
about 1100° C., as the reduction temperature varies 
with the character of the ores and the zine oxide to be 
produced, as well as the reducing carbon—some ores 
being easier to reduce than others. 

24 


ZINC OXIDE 25 


‘Zine oxide is insoluble in water, will not change its 
color when exposed to temperatures ordinarily met in 
commercial uses of this pigment, and is unaffected by 
light, cold or darkness—or wind, rain, and gases 
found in rather concentrated quantities about industrial 
centers. 

Zine oxide has a very fine particle size, being the 
finest paint pigment in common use, and for rubber 





Fig. 3.—Relative size of zinc oxide particle and the space of a 300- 
mesh screen. 


compounding it is considered second to carbon black in 
fineness. It has such a fine particle size that the highest 
powered microscope must be used in order to see any 
of the outline of the individual pieces. The relative 
proportion of a particle of zinc oxide can be shown by 
representing it as a small square in the center of a mag- 
nified space between the wires of a 300-mesh screen. 


26 ZINC OXIDE 


Upon looking through the microscope at different 
pigments the comparative size of the particles can 
easily be seen, and it will become evident that zinc 
oxide varies considerably from the other white pig- 
ments, and even the different zinc oxides will vary as 
against similar pigments produced by a different 
process. 





Figure 4.—Photomicrograph of French Process Zine Oxide 
(3000 Diameters) 





Fraure 5.—Photomicrograph of American Process Zine Oxide 
(3000 Diameters) 





Figure 6.—Photomicrograph of Lithophone (3000 Diameters) 





Figure 7.—Photomicrograph of Sublimed White Lead 
(3000 Diameters) 





Figure 8.—Photomicrograph of Corroded White Lead 
(3000 Diameters) 





iameters) 


h of Barytes (3000 D 


icrograp 


.—Photomi 


FIGURE 9 


CHAPTER 4 


FRENCH PROCESS ZINC OXIDE 


The Manufacture of Spelter 


The French Process, or the “‘ indirect process” of 
manufacturing zinc oxide was first used in France by 
LeClair and Sorel during the latter part of the eigh- 
teenth century. In this process the zinc is reduced 
from the ores to a metallic state. The spelter, or slab 
zinc, is then used in the second step by being vapor- 
ized in a specially constructed furnace and the vola- 
tilized zinc allowed to come in contact with an oxidizing 
atmosphere. The zinc oxide thus formed is cooled 
and collected by means of a baffle plate chamber and 
later muslin bags. Inasmuch as the manufacturing of 
spelter or slab zinc is necessary for the first step in the 
production of French Process zine oxide it shall be 
briefly described. 

Spelter, or metallic zinc, is produced from zinc ore 
by the process of distillation. ‘The zinc ore is mixed 
with coal, charged into a cylindrical clay retort, heated 
to 1200° C., where the zinc is vaporized and allowed to 
cool to about 600° C. and condense to the metal in a 
separate clay “‘ condenser.’”’? The metal is drawn from 
the condensers while in a fluid state and cast into slabs, 
where it cools, crystallizes and becomes the commercial 
product—spelter. 

27 


28 ZINC OXIDE 


The furnace used for smelting zine ores is composed 
of two sections, the base or the heat regenerating cham- 
ber is one section and the laboratory or the upper half 
of the furnace is the other section. In the laboratory 
are suspended the retorts used in the smelting of zine 
bearing ore. 

There are many different types of furnaces used for 
the smelting of zinc, such as the Belgium, Carinthian, 
English, Rhenish, Silesian, and many types bearing the 
names of their designers. In principle they are the 
same. In order to demonstrate the process and to give 
the reader some conception of the process and principles 
involved a brief description of the Convers and De- 
Saulles Furnace, used in this country, shall be given. 

The lower section of the drawing can be seen to be 
the base or preheating section of the furnace. This pre- 
heating section has a height of 14 feet 6 inches, it is 
17 feet 6 inches wide and has a length of 35 feet 4 
inches. It is constructed of heavy fire brick and 
masonry, and it is so arranged that it has two chambers 
containing checker work of brick. A series of gas and — 
air inlets and outlets are arranged to conduct air and 
gas to and from the upper section, called the “ labora- 
tory ’’ where combustion takes place. 

The operation of the pre-heater is solely for the pur- 
pose of pre-heating air before it is led to the laboratory. 
Air is forced through one side of the brick checker 
work (which is very hot) and in coming in contact with 
the hot bricks it absorbs heat. It is then led to a dis- 
tributing main and allowed to enter the laboratory 
of the furnace through an opening at the base of the 
center wall of the laboratory. It is then distributed 
to a series of outlet ports through which it escapes to 


— 
Gnuize tse [NE 


NJ Sl SOS Se 
ae saga a ae ei Sea ee a | a 

















N s Ss a | Esa Sl aad Se aE (SS 6 Se ea * 
= rs ry \_] J = 
IS 
S 











30 ZINC OXIDE 


the combustion section of the laboratory. Gas is led 
through a separate main and sent through distributing 
sections to laboratory outlets just above the air ports. 
Combustion takes place and the gas is burned to fur- 
nish a temperature of about 1200° C. to 1300° C. neces- 
sary for the smelting of the furnace charges. The 
burned gases are led from the laboratory through ports 
in the center wall on the opposite side from the feeding 
ports, and conducted through a separate passage to 
the second section of brick checker work in the base of 
the furnace. The brick checker work absorbs heat 
from the gases and soon becomes very hot. From this 
chamber the gases are led to a stack and allowed to 
escape to the air. During this procedure the one sec- 
tion of the recuperating checker work is being cooled 
by the ingoing air and the other is being heated by the 
spent gases, so that the procedure of reversing the flow 
of the burned gases and air every fifteen minutes permits 
the recuperation of waste heat of the burned gases and 
increases the efficiency of the fuel, by preheating the 
air. 

The gas consumed in the furnaces is made from coal 
by the use of gas producers. ‘There are also several 
types of gas producers, such as the Hegler, the Chapman 
and the Hughes. They are upright, cylindrical, brick- 
lined sheet-steel retorts having a revolving body the 
ends of which are water sealed into a top and a bottom 
section. At the top the revolving jacket is sealed into 
a specially constructed iron cover, which has the feeding 
hopper through which ground soft coal is fed, poke 
holes allowing the use of bars to break up any clinkering 
on the inside of the producer, and the gas lead off. 
The bottom of the revolving jacket is water sealed 


FRENCH PROCESS ZINC OXIDE 31 


into a funnel-like section for the collection and removal 
of ashes. Just above the funnel-like bottom there is a 
hearth upon which rests a bed of hot coals and through 
which air and steam are blown. 

The air and steam being forced through the bed of 
hot coals oxidizes some of the coal and causes chemical 
changes in the upper section of the producer. The 
reaction of 2H20=2H2—O2—C—CO takes place. 
The carbon dioxide that forms passes through the 
coals and becomes carbon and carbon monoxide. The 
main gas stream led from the producers also contains 
oxygen and methane. The producer is designed to 
produce carbon monoxide gas but actual analysis of the 
gas shows the CO to be only about 25 per cent to 30 
per cent of the total. The gas also contains about 
4 per cent COz2, 12 per cent He, and 57 per cent N. 

The laboratory or the upper section of the spelter 
furnace is composed of a firebrick shelf section built 
up through the center. ‘This section serves to support 
the one end of the retorts as well as the center of the 
arch over the top of the furnace. The sides of the 
laboratory are constructed of cast-iron frames and fire- 
brick, having the frames anchored at the base of the fur- 
nace and bound together by rods across the top. The 
arched ceiling of the laboratory is supported both by 
the bound sides and the center wall. 

Retorts are suspended in the laboratory, the base or 
the closed end of the retort being set on the shelves of 
the brickwork in the center wall and the open end being 
supported by the front of the furnace. ‘These retorts 
are arranged in rows and tiers on both sides of the fur- 
nace, having 120 or 130 retorts to a side, or 240 or 260 
to a furnace. 


Se ZINC OXIDE 


The retorts are oval in shape and made of fire clay. 
They are 57 inches long inside and 9 inches high and 
7 inches wide and have a volume of 1.62 cubic feet. 
They are made in a special refractories plant from bond 
clay, grog, etc. The grog used is composed mainly 
of pre-used materials such as broken saggers, brickbats, 





Fig. 11.—View of ‘the inside of a zinc smelting furnace. Note the 
center section, the air and gas ports, the arched ceiling, and the 
side frames. 


etc. The material is crushed, screened, put through 
pug mills for thorough kneading, aged, re-pugged and 
moulded into retorts by large hydraulic pressing 
machines. ‘These vessels are dried for a period to free 
them of as much moisture as possible, later brought to 
the furnace floor where they are placed in a baking 
chamber for the purpose of driving off any chemically 
combined water and to strengthen them so that they 


FRENCH PROCESS ZINC OXIDE BB 


can withstand the intense heat of the laboratory, and 
are brought to a red heat so as to be ready for use in case 
any replacements are necessary for the breakages in the 
furnaces. The retorts are set in the laboratory by 
means of bars and are so arranged that the base or 
closed end is 4 inches above 


the level of the fore or open “SS “SSSSEEEER 
end. 
Another important part of a 


the furnace is the condenser, a_ 
bottle-like clay cone which is set 
at the open end of the retort to SS 
collect, cool and condense the Qe 
Beeyspors 9t0 «metallic Zinc. 4. 19.-Zine furnace con- 
The condensers used are about denser. 
2 feet long, have 7? inches O.D. 
at the base and 44 inches O.D. at the other end. 
Condensers are made of the same clay as are retorts, 
are moulded by machine, have 
the base crimped so as to fit 
—Al into the mouth of the retort and 
$5 are burned at a temperature of 
eee = Condentersup: 900° ©.. There is a condenser 
port. for each retort, and they are 
_ suspended in the open air by a 
hinged iron bracket attached to the side of the cast- 
iron furnace frames. 

The raw material, or charge, used for the production 
of spelter consists of zinc ore in proportion of 18,000 
pounds, dust coal 7000 pounds and common salt 40 
pounds. ‘This charge is churned to an even mixture 
in a Ransome concrete type of mixer, taken by a special 
skip to a storage bin, from which it is later drawn into 


34 ZINC OXIDE 


charge larries which carry it to the furnace floors. 
The charging car, on which the larries deposit the 
charge, is a flat table-like platform, having four wheels 
permitting it to be rolled forward from the back wall of 
the furnace building to the face of the furnace at the 
time it is desired to charge the retorts. 

The discharging and recharging, as well as the entire 
operation of the furnace, are carried on by manual labor 
and as the filling and handling of the retorts must be 
done individually by laborers, the operators are sub- 
jected to intense heat during the time of this laborious 
task. 

A charge crew of six men remove the hot condensers 
from the face of the furnace by means of condenser rods. 


oe 


Fic. 14.—Condenser rod. 


The condensers are set aside and when cool will be 
cleaned by a member of the crew. Droppings and the 
old ore-coal mixture of the former charge are scraped 
from the front of the retort, and saved for a later re- 
charging. A sheet-metal shield is dropped over the 
front of the furnace and under its protection a member 
of the crew inserts a long pipe into the retort, and by 
means of a hose attachment to the pipe he introduces 
water into the back end of the red-hot retort and by the 
formation of steam at that point in the retort the old 
charge is ‘“‘ blown out.’ 

This is done to all of the retorts. ‘The refuse drops 
to the floor and then through hopper openings in the 
floor at the side of the furnaces. Further cleaning of 


FRENCH PROCESS ZINC OXIDE 35 


the retorts is then done by chisels if necessary. Break- 
ages are removed by means of hand bars and new 
retorts are inserted. After the furnace is discharged 
and the floor is cleaned the charging table is rolled 
to the front of the furnace and the men proceed to 
charge the retorts. 

The mixture of coal, ore and salt is thrown into the 
retorts by means of a special scoop shovel. The men 
throw the charge into the retort until it becomes full 
and then run a rod through the top of the charge to 


Fria. 15.—Blowout pipe and hose. 


permit the outflow of gas and prevent a blowout. It 
takes three and one-half hours to discharge and re- 
charge a furnace. 

The retorts being filled the condensers are then 
placed. ‘They are placed by forcing the crimped larger 
end of the condenser into the open end of the retort 
and then resting the neck or fore part of the condenser 
on the “‘ grasshopper arms ’”’ or brackets which pro- 
trude from the front of the furnace. The openings of 
the condensers are luted or sealed shut by moist mix- 
ture of coal and ore in order to seal off any outside air 
but at the same time to allow internal gases to escape. 
Carbon monoxide gas is generated inside the retort and 
does escape through this luted mouth of the condenser. 
Being a poisonous gas it is desirable that it be destroyed 
and for this reason the gas is burned at the mouth of 
the condenser. In burning with a bright yellowish 


36 ZINC OXIDE 


flame the gas causes each condenser to appear as a 
lighted torch, giving the furnace block, with 120 or 1380 
flaming condensers to each side, a very unique appear- 
ance, and especially so at night. 





Fic. 16.—Zine furnace in operation. Note the condensers and 
the burning gases issuing from them. 


The action of the charge within the retort varies 
directly with the temperature. . The reduction of zinc 


FRENCH PROCESS ZINC OXIDE aye 


from the ore, by the presence of carbon, does not begin 
until the vessel has reached the temperature of 900° C. 
to 950° C. Thus, during the “ warming up ”’ period, 
the carbon has little effect upon the reduction of metallic 
zinc. However, below the temperature of 800° C. there 
will be a reduction of zinc due to methane, COz formed 
in the charge and hydrogen. ‘The COz2 being abundant 
acts aS an oxidizing agent upon the zinc vapors and 
causes a formation of crude zinc oxide and blue powder, 
commonly known as zinc dust. As the heat of the charge 
increases the relative amounts of COs will decrease 
and CO increase in proportion. ‘The zinc is vaporized 
in the retort and comes to the condenser where it is 
cooled to 600° C., crystallizes or condenses and forms 
metallic zine. 

The furnaces are charged once in twenty-four hours, 
the hours of charging being usually four to seven- 
thirty in the morning. Draws of the metal are made 
three times a day, usually at 2 p.m., 10 P.m., and at 
3 A.M. The zinc is removed from the condenser by 
inserting a scratcher button, which is a rod having a 
blunt end, and drawing the molten zinc into a sus- 
pended movable kettle, which is swung under the 
condensers. ‘The drawn metal is poured into a mixing 
pot and later cast into slabs. 

Slab zinc, commercially called spelter, is used prin- 
cipally for galvanizing sheet steel and for brass manu- 
facturing. A portion of the natural production of 
spelter is rolled into sheets and strips for roofing, etc., 
and still a smaller percentage is used for the manufac- 
turing of French Process Zine Oxide. 


CHAPTER 5 


FRENCH PROCESS ZINC OXIDE 


The Manufacture of Zinc Oxide 


The furnace used in manufacturing French Process 
zinc oxide very much resembles a spelter furnace, as it 
also has a recuperating pre-heating base and a labora- 
tory in which are suspended a row of retorts very similar 
to the retorts used in the manufacture of spelter. 

There are four brick checkerwork recuperating sec- 
tions in the base of the furnace, two of which are vsed 
for gas and the remaining two are used for air. One of 
each set is used at a time for pre-heating, the other one 
being heated up in the meantime by the outward pas- 
sage of burned gases. ‘The flow of the gas and the air 
is reversed every half hour so that the ingoing gas and 
air may be maintained at a high temperature. 

The upper section of the furnace is a brick encased 
combustion chamber, across which is suspended a row 
of muffle. The gases coming from the preheating 
section burn in this combustion chamber giving an 
intense heat around the muffles and causing a constant 
temperature of about 1400° C. The gases, after burn- 
ing, pass down. from the combustion chamber to the 
recuperating brickwork in the base and then out to a 
stack. Above the combustion chamber is a separate 
brick compartment known as the gas chamber. Into 

38 


FRENCH PROCESS ZINC OXIDE 39 


this chamber, which is merely a brick rectangular space, 
is fed carbon monoxide gas, which was generated in 
a producer and cleaned in a scrubber beneath the fur- 
nace floor level. The carbon monoxide gas is heated 


PRAY RAT AAS 
: a 


pm N 


a Se ee SS 


h aN 


care) 
Ly | 
SA; 


BEeSBeait 
eos Si SS Oa Bee eS Oe 


e 
a 
a Wik we HERE 


Fic. 17.—French process zinc oxide furnace. 


CMLL GLE SLL a Mee d 


by the warmth of the firebrick partition which is 
between it and the combustion chamber. It is 
removed from the gas chamber by means of a pipe 
leading from an opening in the chamber to the charge 
end of a muffle. 


40 ZINC OXIDE 


The muffle or retort used in the French Process zine 
furnace is the same size and shape as a spelter retort. 
The one end is open while the other end has a dam, or 
half-closed face. The muffle is suspended so that the 
open end extends to the outer surface of the rear sup- 
porting wall of the furnace, and the dam end extends 
to the outer surface of the front supporting wall. 

The fore end of the furnace has a sheet-iron section 
running the entire height of the furnace. It has three 
doors for each section of muffles, one at the level of the 
muffles, one at the level of the base of the laboratory 
and one at the bottom of the furnace. Above the sheet- 
iron section or chamber is a collection pipe, being the 
broad side of a cone which leads to a collection sector 
above. 

The muffles of the furnace are charged with spelter. 
The slabs of zinc are chopped or broken up into con- 
venient sizes and placed in the muffle through the open 
end at the rear of the furnace. A small portion of clay 
is also thrown into the muffle to prevent the metal 
and slag from clinkering to the sides of the muffle at 
the time of cleaning. ‘The usual charge consists of two 
or three parts of high-grade spelter to one or two parts of 
Prime Western (higher leaded) spelter. 

The muffle is not completely filled with spelter, but 
a space of about 3 inches is allowed at the top of the 
muffle for vaporization. After the spelter has been 
placed in the muffle a pipe set in the shape of a U is 
inserted in the gas chamber through an opening in line 
with the muffle. This is done so that a stream of 
carbon monoxide gas may be led to the muffle and serve 
two purposes, namely, prevent oxidation in the muffle 
and to lead the zine vapor to the mouth of the muffle. 


FRENCH PROCESS ZINC OXIDE 41 


After the pipe is set in the muffle opening the back of 
the muffle is then closed with clay, the plastering being 
made to conform to the pipe and made so as to seal the 
end of the muffle. The clay is tamped and made secure 
in place by means of a red-hot blunt-ended rod. 

The zine contained in the muffle soon melts and as the 
temperature rises it vaporizes. The zinc vapor is 
induced to flow to the front end of the muffle by the 
stream of carbon monoxide gas and there it comes in 
contact with air or an oxidizing atmosphere and 
“burns ”’ with a bright yellowish flame to zine oxide. 
The front end of the muffle is the only means for check- 
ing the contents of the muffle. As soon as the flow of 
zinc oxide begins to decrease it is obvious that the 
charge is becoming exhausted. 

After the charge of spelter has been fairly well reduced 
and the amount of the zinc in the mufile is getting low, 
a second charge is made. This charge is of molten 
metal which has been brought to the side of the fur- 
nace in a ladle. A slide, placed in the end of the gas 
_ pipe, is opened and a tray-like funnel is inserted. The 
molten metal is thus poured into the muffle and the 
proper amount of zinc is charged. These molten 
charges are made as often as are necessary. It is 
arranged, however, so that the muffles can be opened 
and cleaned once in forty-eight hours. 

The cleaning of the muffles is done in order to 
remove any of the impurities which form in the muffle 
and cause a decrease in the production. The charging 
‘end of the muffle is chiseled open and all of the clay 
removed. The gas pipe is removed and disconnected 
from the gas chamber. The muffle is then scraped 
clean by means of a spoon-like rod which reaches to the 


42 ZINC OXIDE 


other end of the muffle and draws all refuse material 
back with it. There may also be a clinker formed at 
the side of the muffle which will necessitate chiseling 
in order to remove it. The refuse from the muffle is 
dumped on the charge floor, allowed to cool and then 
stored for shipment. This refuse contains about 40 
per cent zinc and 20 per cent lead and can be used in 
the manufacture of leaded zinc oxides. 

There are many breakages of muffles due to the 
deterioration from the charge, from the intense heat, 
and from the wear and tear caused by cleaning. A 
furnace usually has twenty muffles and has about 
eighty replacements a month. Zinc saturated sections 
of broken muffles are recovered and used for spelter 
or zinc oxide charges. 

The stream of zinc vapor pours from the open end of 
the muffle and there combines with the oxygen of the 
air and forms zine oxide. The stream of zinc oxide, 
now appearing as a dense snow floated in air, is drawn 
up from the furnace to a collection main and led to 
the main collection hopper. A small portion of the 
zinc oxide falls to the catch hoppers at the base of the 
collection main, from where it is removed, screened 
and used in the main products of the plant. 

Accretions, known as horns, form at the fore end of 
the muffle. These horns, or hardened and fused accu- 
mulations of zinc oxide, act as condensers to the zinc 
vapor coming from the muffle and may cause the 
vapor to remetallize and form metallic zine as a coating. 
In order to stop this action a man is located at the base 
of the iron section in front of the furnace and by means 
of a long rod having a scraper he keeps the face of the 
muffle scraped clean of oxide horns. Any horns that 


FRENCH PROCESS ZINC OXIDE 43 


form are scraped off and fall to the base of the sheet- 
iron section and are then collected at the base floor 
level. 

From this accumulation of horns and zinc oxide 
scraped from the muffle face is reclaimed some rough 
oxide. ‘This is done by having the accumulated scrap- 
ings dumped into a large screen where the heavy horns 
are removed. ‘These horns are segregated, barreled 
and are later used in the manufacture of another white 
pigment, lithopone. The zinc oxide passing through 
the screen falls to the base of an elevator chain which 
carries it toa trommel above. Here all of the fine horns 
* and heavy particles are removed. The zinc oxide is 
allowed to fall into a blowing section, and the blast 
carries the light oxide from this cleaning station to a 
bag collection unit. All of the refuse or heavy zinc 
oxide and horns collected in this cleaning process 1s 
barreled and later shipped away for the use in making 
lithopone. 

To return to the furnace—the main stream of zinc 
oxide is led through a large sheet iron pipe to a large 
collection hopper. The collection hopper is a large 
oblong sheet metal chamber with baffle plates extending 
from both top and bottom. The baffle plates are so 
alternated that the incoming zinc oxide streams must 
follow a zigzag course, hitting the plates and the sides 
of the collection chamber at every turn. The heavier 
zine oxide falls first and the lighter zinc oxide is car- 
ried to the further end of the hopper. The zinc oxide 
that falls to the bottom of the collection chamber is 
removed by means of hopper doors, as the bottom of 
the chamber is arranged as a series of small hoppers. 
A lead off pipe at the far end of the hopper allows the 


44 ZINC OXIDE 


zinc oxide still remaining in suspension to be led to the 
secondary collecting unit. 

Leaving the collection chamber the air, still heavily 
laden with zinc oxide in suspension, is fed to a blow fan 
—the agency of action for the stream—and from it is 
forced into collection bags. The bags used are made of 
muslin and are about 3 feet in diameter and hang 





Fig. 18.—Collection chamber. Showing baffle plates and hoppered 
bottom. 


20 feet long. They are attached at the top to round 
outlets in the iron pipes and are kept closed at the 
bottom by strings or knots. The interstices of the col- 
lection bag’s muslin allow the air and gases to escape 
but imprison the zinc oxide particles. The zine oxide 
clings to the side of the bag, is shaken loose periodically 
and is caught at the bottom of the bag where it is col- 
lected and taken in bags to the mixing room. 

The zine oxide that collects at the further end of the 
collection chamber and at the bags is always the lightest 
and fluffiest and finest in particle size. It contains a 
large amount of “ imprisoned ”’ air and is consequently 


FRENCH PROCESS ZINC OXIDE 45 


lighter in specific gravity and less bulky than the other 
zinc oxides. It is also very clean and free from dirt. 
This being the first grade zinc oxide it is classified as 
White Seal. It is blended to assure conformity to a 
standard sample, bolted through a flour bolter to have 
it thoroughly cleaned of any fibers or foreign matter, 
and is then packed in 150-pound barrels. 

The zinc oxide collected at the central section of the 
collection chamber is more dense, and the zinc oxide 
collected at the first part of the collection chamber is the 
heaviest of all. It will be noted that there is no chem- 
ical difference in the gradings of this zine oxide, but the 
grades of French Process zinc oxide differ solely in their 

physical properties, such as gravity and color. If 
cadmium is present in large degrees in the spelter of 
duplication the charge it will cause the zinc oxide to 
appear yellow. 

The zinc oxides, classed as Green Seal and Red Seal, 
taken from the collection chamber are then subjected 
to a special heat treatment to give them a denser body. 
The collected pigment is elevated to a platform and 
allowed to fall through a superheated brick vertical 
muffle. 

The muffle used in the reheating of the zinc oxide is 
made of brick, having a height of 30 feet, and has a 15- 
inch square opening running the entire height, the open- 
ing being divided into three sections by two brick divid- 
ing walls. ‘The muffle walls are heated by being encased 
in a fire-box. ‘The zinc oxide is poured into a hopper 
at the top of the muffle and from it is fed by a revolving 
cylinder grate so that the amount going down the 
muffle is not greater than the temperature of the muffle 
can care for. ‘The zinc oxide falls like snow and as it 


46 ZINC OXIDE 


falls is heated. ‘The heat causes the zine oxide to 
become compact and frees it of a large percentage of 
the imprisoned air. At the bottom of the muffle the 
zinc oxide falls, red hot, on a wide flat pan-like truck. 
The truck is so devised that the zine oxide cools readily. 
As soon as it is cooled it is taken to the mixing bins and 
there allowed to cool to the normal temperature. It is 
blended to meet a standard sample, bolted and packed 
into 50-pound bags or 300-pound barrels. 

French Process zine oxide is used principally for 
making white and tinted enamel paints. Its uniform 
very fine particle size and good color especially recom- 
mend it for this use. It is also used to some extent 
in outside white paints. The pottery manufacturers 
use it in the compounding of their vitreous glazes. 
Manufacturers of cosmetics also use this grade of zinc 
oxide, generally White Seal, for face powders. Recently 
rubber manufacturers have been using large tonnages 
of this grade of zinc oxide in rubber compounding. 

It is generally agreed that the best French Process 
zinc oxide of the world is made in the United States. 
Imported French Process zinc oxides vary chemically 
and physically, especially in sulphur content, while © 
American production is standard and uniform. Great 
developments may be anticipated in the American pro- 
duction of this product, principally because of the 
exacting demands of the rubber manufacturers and the 
severe competition that other mineral pigments are 
giving for this use. 


Pharmaceutical Zinc Oxide 


Pharmaceutical zinc oxide is made by the French 
Process. A few variations in the actual operation of a 


FRENCH PROCESS ZINC OXIDE 47 


plant are made because U. S. P. zinc oxide is the best 
zine oxide made both chemically and physically and 
every possible precaution is taken to assure purity. 





La 





Fic. 19.—Pharmaceutical Zine Oxide Furnace. 


LODE SE NN 





The furnace used to produce this grade of zinc oxide 
does not have a recuperating section, and does not use 
gas as fuel, but is heated to a temperature of about 


48 ZINC OXIDE 


1200° C. by means of two coal-fed fire-boxes placed 
at each end of the brick furnace structure. ‘Thus the 
furnace very much resembles a fire-box, fed fuel at 
both ends and having a row of muffles or retorts 
extending side to side and placed near the top of the 
furnace. | 

The muffles are similar to the retorts or muffles used 
in the making of spelter or French Process zine oxide, 
having a capacity of 1.28 cubic feet of molten zinc. 
The muffles are kept at a constant temperature, being 
fed a “stick” of spelter every ten minutes. These 
sticks of spelter are especially selected for this use 
because of chemical composition and are cast so as to 
facilitate charging of the muffle. 

The zinc oxide which forms at the mouth of the muffle 
is drawn up through a collection downcomer, to a fan 
and forced from there to a bag house where it is col- 
lected in the meshes of muslin bags. It is packed 
directly from the collection bags to well-lined barrels. 
Only 100 pounds of U.S. P. zine oxide are packed 
loosely into a large barrel. 

Pharmaceutical zinc oxide is used exclusively for 
medical purposes—such as zinc ointment, healing pow- 
ders, etc. It has a very high antiseptic value. It is 
also used in some of the higher grades of face powders. 


CHAPTER 6 


AMERICAN PROCESS ZINC OXIDE 


The American Process, or direct process, of manufac- 
turing zinc oxide has been used since 1852. It is called 
the American Process because it was invented and devel- 
oped in this country. The principle of the process is to 
vaporize the zinc directly from the ore, the reduction 
being facilitated by carbon, and then allowing the zine 
vapor to oxidize. In the process a mixture of zinc ore 
and coal is spread on a body of burning coal, which, in 
turn is on a perforated grate, and an excess of air is 
blown through the grate. The heat of the burning coal 
and the reducing action of the CO gas causes the zine 
to volatilize and it burns to zinc oxide by the combina- 
tion with the excess of air in the upper part of the fur- 
nace, and in the lead off flues. The zinc oxide with all 
of the products of combustion from the furnace, and 
the excess of air, is carried to a bag room through a 
carrying system of pipes which also act as cooling 
agents. In the bag room the gases escape through the 
meshes of the muslin bags, while the zinc oxide becomes 
entangled and is screened out or imprisoned in the bags. 

There are two distinct types of furnaces used for 
producing zinc oxide by the American Process, known 
as the Eastern Type and the Western Type. ‘There 
are also combinations and variations of the two, as 

49 


50 ZINC OXIDE 


well as several new types of furnaces that represent 
indicative trends for the future. The largest and 
newest plant producing zinc oxide by the American 
Process is located in the East, about one hundred miles 
inland from New York City. A description of the plant 
and an outline of the procedure at this plant will give 
the reader a clear understanding of the American 
Process as practiced in the East. 

The general plan of this Eastern zinc oxide plant— 
the largest in the world—is shown in the accompanying 
drawings. It can be seen that the principal sections of 
the plant are the storage yard, for the ore and coal, the 
stock bins and mixer, furnace, fan house and bag room. 
These individual parts of the plant shall be discussed 
separately and we shall endeavor to trace the complete 
journey of zinc from its reception at the plant in the 
form of raw ore to the departure of the finished product 
in the form of zinc oxide packed in the car. 

Zinc ores and anthracite coal coming to the plant are 
brought up an incline to a two-track unloading and 
storage trestle. ‘The trestle is a long concrete structure, 
being sufficiently wide to accommodate two tracks. 
The incoming cars are propelled by an electric truck 
car and are placed for proper unloading. A concrete 
wall runs through the middle of the trestle and to its 
entire length. This is done so that the track on the 
furnace side can empty cars directly into steel bins 
for current needs while the track on the opposite or the 
storage side of the trestle can empty the contents of 
the cars to an open platform for removal to the outside 
storage piles. 

The trestle also incorporates a concrete foundation 
and a single rail for one set of wheels of a large 233-foot 








AMERICAN PROCESS ZINC OXIDE 


























‘1a. 20.—Crossesection view of zinc oxide plant at Palmerton, Pa. 


ol 


52 ZINC OXIDE 


gantry crane. The crane has a 5-ton bucket and a 
working radius of several hundred feet. Ores and coals 
for long storage are piled by the crane, and later, when 
needed, are brought back to the trestle by means of the 
crane and this time placed in the current material bins. 
It is generally considered good practice to store some 
ores for a period as they need weathering, and by this 
weathering they become more uniform as to their 
moisture content. 

Current materials are taken directly from the cars 
and fall to bins on the furnace side of the trestle. The 
cars are all unloaded by opening the bottom hoppers 
and allowing the material to fall through the iron 
gratings into Brown tangential bins. As the materials 
are unloaded they are sprayed with water from above 
the car. This is done in order to have the materials 
well soaked, which permits easy handling and is desir- 
able for cohesion of the charge in the furnaces. In cold 
weather this watering is done away with as snow and 
general weathering give sufficient moisture. Steam 
is generally used to melt the frozen ores and coal and 
this also imparts moisture to the materials. 

Samples of all incoming materials are taken from the 
car at the time of unloading. The samples are taken 
according to standardized methods, giving a repre- 
sentative average of the car. ‘These samples are then 
taken to a special sample house, a brick and steel 
building, equipped with driers; compact, rotary and 
grinding types of crushers and bottling facilities. The 
samples are first laid out on a long wide iron tray and 
placed in a drying room where they are thoroughly 
dried. After drying they are crushed to a granulated 

size—the ore so that it will pass through a 100-mesh 


AMERICAN PROCESS ZINC OXIDE 53 


screen and the coal through an 80-mesh screen. The 
samples are then bottled and placed in a steel carrying 
case to be sent to the laboratory for analysis. 

The tangential bins are so arranged that their dis- 
charge outlets are directly over a larry track. Each 
bin has six gate outlets, operated automatically by an 
arm on the larry car. The bins, being steel, freeze up 
very easily in cold weather and to prevent this as much 
as possible steam pipes are run along the outer surface. 
A scale hopper larry car runs along below the bins, taps 
the charges from the bins and carries the proper amounts 
of the various materials to the mixing stations and there 
discharges the contents of its bins. 

Mixing of the ores and coal is accomplished by having 
three mixing stations, each of which has two Ransome 
mixers. ‘These mixers are located at a level below the 
larry track. ‘The larry drops the ores and coal to a 
bin and from there it is fed to the mixers. The mixers 
are revolving cylinders, with interior blades that toss 
and mix up the contents and finally carry it to the 
opposite end where it falls into a trough leading to a 
skip. ‘This is the only process that the raw materials 
are subjected to before being used in the furnaces. 

The mixed coal and ore coming from the mixer falls 
into the skip. One charge for the furnaces, known as 
the firing coal charge, is placed directly above the skip 
and may be tapped directly into the skip without going 
through the mixer. The skip is a rectangular steel 
car having the contents of one furnace charge. It runs 
by means of small iron wheels upon a railed incline, 
being propelled by means of an iron cable actuated 
by pulleys and electric motor. At each of the three 
mixing stations there are two mixers, two skips and 


54 ZINC OXIDE 


thus two runways up the incline to the top of the 
furnace building. 





(Courtesy of Ransome Machinery Co.) 
Fig. 21.—Mixer used for preparing the furnace charge. 


The empty skip coming down the one track acts as a 
counterbalance to the loaded skip ascending on the other 
track. The skips are dumped at the top of the fur- 





(Courtesy of Ransome Machinery Co.) 
Fig. 22.—Skip ear. 


nace building by having the front wheels follow a 
descending track while the rear wheels are allowed to 


AMERICAN PROCESS ZINC OXIDE no 


remain on an outer and ascending track, lifting the rear 
of the skip to an inverted position. The contents are 
dumped into furnace bins near the top of the furnace 
building. 

The furnace bins are large wood and steel structures, 
located at the top of the furnace building and in the 
center of the row of furnace blocks, enabling the dis- 
charge of material to both sides of the furnace building, 





Fig. 23.—Furnace bins and skip. 


There are four furnace bins for each skipway and thus 
eight bins for each mixing station. The bins have four 
compartments, three of which are used for the various 
ore charges and one for the coal charge. The material 
comes down from the skip over a distributing slideway 
which guides it to the proper bin. These bins are not 
intended to be storage places for materials and never 
carry any surplus mixtures or coals, but are being con- 
stantly emptied by the furnace charge cranes, and are 
refilled as soon as emptied. 


56 ZINC OXIDE 


The charge crane is a hopper crane running on an 
elevated track along the side of the furnace building 
and above the level of the furnace hoppers, which, in 
turn, are located directly above the furnace blocks. 
The charge crane acts as a transfer agent for the mate- 
rial from the furnace bins to the furnace hoppers, which 





Fic. 24.—Charge crane. Located above the furnace hoppers. 


in turn dump the charges of material directly into the 
furnaces. At each charging station directly below the 
furnace bins are four furnace bin gates for each side of 
the furnace, or an outlet for each furnace bin compart- 
ment. ‘Three of the bin lead-outs are for ores and are 
extended further than the fourth which is for the coal 
charge. The gates are opened by means of an air- 
operated rod and a definite amount of material falls to 
the weighing hoppers of the charge crane. ‘The material 


AMERICAN PROCESS ZINC OXIDE 57 


falls into a partitioned hopper, one side for coal and the 
other for ore. 

The charge crane deposits the ore and coal mix- 
tures into the furnace hoppers, which in turn are 
arranged directly above the furnaces, one furnace 
hopper being arranged for each furnace door. The 
furnace hopper very much resembles the partitioned 
hopper of the charge crane as it has a partition 
through the middle, the inner compartment being for 
coal and the outer compartment for the ore charge. 
It tapers, as do all hoppers, to the bottom and at the 
termination of the neck it has a gate, which when 
Swung in one direction opens the coal chamber and 
when swung oppositely it opens the ore charge section. 

The furnace building of the plant is a steel structure 
extending about three-fourths of a mile, and is 35 feet 
wide. It houses thirty-eight furnace blocks. The 
furnace floor of the building is about 12 feet above 
ground level. ‘This is done so that cars may be run 
under the furnace floor to receive and carry away the 
clinker or residues from the furnaces. 

There are three types of the Eastern American 
Process style of furnaces used at this plant, namely 
the tunnel type, the four-furnace type and the six- 
furnace type. Structurally all of the furnaces are 
of the same measurements. Each furnace block has 
the same exterior measurements as all others. The dif- 
ferences in the types mentioned above come from the 
partitioning of the inside chamber of the furnaces. 

The furnace blocks are “‘ blocks”’ of firebrick, and 
masonry strengthened by steel rods and girders. ‘The 
blocks are 45 feet long and 16 feet 6 inches wide and 7 
feet high. ‘The interior of the furnace contains a fur- 


58 ZINC OXIDE 


nace grate upon which the charge is placed and burned 
off, and an arched ceiling. In a four-furnace block, the 
interior of which is partitioned off into four separate 
and distinct furnaces, each furnace has hearth area of 
19 feet 63 inches by 5 feet 114 inches. In the roof or 
ceiling of each furnace are three charge openings and 
two lead-off pipes 20 inches in diameter for the with- 
drawal of the zine oxide laden gases. On the side or 
the face of the furnace are three working openings 
closed by doors. ‘The hearth of the furnace is made of 
cast iron, either slotted or pin-hole grate bars. Below 
this is an ash pit constantly sealed with water to keep 
the hearth cool and through which is fed a blown draft 
of air. 

In the operation of the furnace, supposing a charge 
having run for eight hours and being fully worked off, 
the stream of gases is cut off from the collection pipes 
by means of a butterfly valve just at the base of the 
flue. The ashes that were piled at the door or working 
opening to close the doorway are removed and thrown 
aside to be used again. The residuum remaining 
in the furnace after the charge has been worked out is 
in the form of luminous tough porous clinker. ‘This red- 
hot clinker covering the whole grate is broken up by 
heavy hand slice bars and raked out of the furnace 
through the doors and dropped through an opening 
or doorway of the building floor, into cars below. ‘The 
back walls of the furnace are then chiseled free from 
adhering clinker and the hearth is cleaned. ‘The clean 
grate is quickly covered with coal dropped through the 
charging neck from the furnace hopper above. ‘The 
doors of the furnace are closed and a small amount of 
draft is admitted through the ash pit. This is done 


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AMERICAN PROCESS ZINC OXIDE 


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60 ZINC OXIDE 


in order to heat up the coal bedding which will be used 
as the smelting medium for the next charge. When 
the bed of coal burns evenly and brightly the charge of 
ore and coal mixture, which is in the furnace hopper, is 
dropped into the furnace and spread out evenly over 
the whole grate area by means of long rakes. This 
burden usually runs 6 inches to 9 inches deep and will 
weigh about 55 pounds to 60 pounds per square foot. 
The temperature of the furnace at this point is about 
700° C. The doors of the furnace are then closed by 
piling ashes on a suspended shelf of sheet iron, and 
the air gradually admitted under the grate until the 
whole charge is well ignited. 

The draft or the 2-inch or 3-inch pressure of air that 
furnishes the cold blow to the ash pit is furnished by 
means of centrifugal electrical fans housed in a special 
fan house at one side of the furnace building. ‘There 
is one fan for each furnace block. The draft is led 
from the fans through 12-inch sheet-iron tubing directly 
above the center of the block, where a main carries it 
down the length of the block. At each furnace door- 
way, or opening, branches of the air pipe come down 
the side of the furnace to the ash-pit door, where it is 
fed to the furnace, going up through the grates to aid 
in the combustion of the coal and to furnish oxygen 
for the formation of zinc oxide. 

The charge within the furnace gradually rises in 
temperature, the gases of the combustion being led to 
the air because of the butterfly valve in the base of the 
flue, or discharging neck. After an hour or so the gases 
pouring from the furnace begin to show a yellowish 
color, tinged with green. ‘The workmen call this flame 
‘“‘ zine candles.” The early gases coming from the fur- 


AMERICAN PROCESS ZINC OXIDE 61 


nace have a purplish color, being burning carbon mon- 
oxide gases. As the color of the flame grows to a 
deeper yellow it indicates that the reduction of the zine 
and the formation of zinc oxide is progressing. After a 
while the flame becomes a deep yellow, tinged with 
green. ‘This indicates a good oxide stream so the 
damper of the butterfly valve is closed and the stream 
of zinc oxide and gases allowed to be drawn upward 
through the collection pipes, called the down legs. _ 

The charge burns for eight hours, the color of the 
gas stream passing upward through the damper indi- 
cating the stage of the fire and the grade of zinc oxide 
the furnace is producing. Sometimes the furnace 
will not produce good zinc oxide due to the fact that 
the charge may have been dropped before the fuel 
charge was sufficiently heated—thus a chilled fire, and 
consequently a poorer grade of zinc oxide. Again 
there may not be sufficient sulphur within the charge 
to sulphate the lead and cadmium and thus cause 
pinkish and yellowish discoloration of the pigment. 
The pressure of the cold blow draft is another influ- 
ential factor upon the production and operation of the 
furnace, too much pressure may cause blow-holes in the 
charge allowing too rapid reduction in one location, 
overheating the grates and producing a variety of 
undesirable results. 


Chemistry of the Formation of Zinc Oxide 


The exact chemical reactions within the furnace at 
the time of the formation of zinc oxide are not known. 
The heat of the charge rises to 1100° C. to 1800° C. 
and it is practically impossible to have knowledge 


62 ZINC OXIDE 


of the actual reactions. It is presumed that the zinc 
content of the ore and the carbon of the coal unite 
to form CO and Zn. Continuing further the Zn and the 
CO form Zn and COQz, the COz combines with the Zn 
forming ZnO and CO. The CO gas thus formed acts as a 
very strong reducing agent upon the ore and increases 
the temperature of the furnace. ‘The hydrogen of the 
water in the charge is also liberated by virtue of the 
oxygen content combining with Zn to form ZnO. The 
ores also contain a quantity of cadmium and lead and 
as these metals are volatilized they are also oxidized. 
Too much lead oxide, being yellowish and reddish in 
-color, causes discoloration of the zine oxide. ‘The 
cadmium oxide is also distinctly yellow. However, 
these oxides of lead and cadmium are kept to a mini- 
mum by the action of the sulphur contained in the ore 
and in the coal. Sulphur, having a greater affinity for 
lead and cadmium, forms lead and cadmium sulphates, 
which are distinctly white. It is undoubtedly a fact 
that a portion of the zinc is also sulphated, but not to a 
great extent because chemical laboratory control of 
raw materials only permits enough sulphur to be used 
in the charge to afford proper care of the lead and cad- 
mium. If any appreciable quantities of zinc sulphate 
form they are undoubtedly reduced to zinc oxide and 
to sulphurous anhydride, the latter completely escap- 
ing. Chemical changes are aided by the several agencies, 
such as the combustion of the coal mixed with the ore, 
the'carbon monoxide formed in the furnace, the hydro- 
gen liberated from the water of the mixture, and}the 
exothermic reaction of the oxidation of the vaporized 
zinc. ‘lhe oxidation of the zinc is supposed to take 
place near the ceiling of the furnace. 


AMERICAN PROCESS ZINC OXIDE 63 


It was previously mentioned that there were three 
types of Eastern American Process zinc oxide furnaces 
used at this plant. Namely, the four-furnace type, 
the tunnel type and the six-furnace type. 

The four-furnace type of block is characterized by the 
fact that it has four distinct furnaces within the block, 
the interior of the block being quartered. As all fur- 
nace blocks have six doors on each side there are three 
doors for each furnace, three charging necks and two 
gas necks. The grate area is 444 square feet for each 


rH rH 


pt 


Fic. 26.—Four-furnace block division. 


furnace. The advantage most cited for the four- 
furnace block is that it fits very nicely into an eight- 
hour shift schedule. It takes eight hours to burn out 
a charge so that by having a crew care for two blocks 
they are able to draw one furnace each hour. It also 
has an advantage in the fact that when a fire is drawn 
the cooling off of the furnace block is only one-fourth 
of the entire area of the block. 

The tunnel type of furnace block is a type having 
the block divided by partitions into thirds. These par- 
titions run from side to side forming three separate 
furnaces. This type of block has two doors for each 
side of the furnace, two charging necks per side and one 


64 ZINC OXIDE 


gas neck for each side, or two for the tunnel furnace. 
The grate area for this type of furnace is slightly greater 
than the four-furnace type as it does not have as many 
dividing walls. The grate area is 496 square feet per 
block. There are a few advantages of this type of 
block, one being that the absence of the back wall 
gives less trouble in drawing the worked-out charge, 
thus facilitating cleaning; another is the fact that 
structurally the tunnel type must have a higher ceiling 
arch, which does not reflect the heat so intensely upon 


et 


-— -—4 


Fig. 27.—Tunnel furnace block division. 


the charge and cause any fusible materials to “‘ glass ”’ 
the grates. There are several disadvantages, such as the 
severe cooling of the oxide stream because of shutting 
off one-third of the block at the time of charging. The 
larger arch also induces a consideration of higher main- 
tenance costs. 

The six-furnace type of block is one in which a cen- 
ter dividing wall has been run down through the funnel 
type of block. Thus there are six distinct furnaces 
made in the one block, each having two doors, two 
charging necks and one gas neck. The furnace, 
although not having such a large grate area as the other 
types, makes a greater ratio or recovery than the other 


AMERICAN PROCESS ZINC OXIDE 65 


furnaces due to the fact that a constant temperature is 
usually maintained and that a constant and even mix- 
ture of the zinc oxide is always flowing into the main 
oxide stream. The six-furnace types are especially 
advantageous in the preparation of leaded zine oxides 
where a high and even temperature is desired. 

The zinc oxide stream drawn from the furnace 
through the gas neck, in combination with the burned 
gases, air, etc., goes directly upward through vertical 
sheet steel pipes, called down legs. The down legs are 


Fig. 28.—Six-furnace block division. 


about 15 feet in height and at the upper end feed the 
zinc oxide into large cylindrical drums. ‘The purpose 
of the drums is to thoroughly intermix the zinc oxide 
coming from the different furnaces of the block, and 
to permit the oxidation of any zinc vapors that escaped 
oxidation in the furnace, as well as to permit the gases 
to cool to some extent. ‘There are either two or three 
drums which receive the zinc oxide first and these in 
turn feed the stream of gases and pigment to an upper 
and common drum. 

By the time the oxide stream is drawn from the drums, 
which are directly above the furnace blocks, it is very 
well mixed. The temperature is about 1000° C., and 
the stream still contains some unoxidized zinc vapors. 


66 ZINC OXIDE 


In order to slowly cool this stream of gases and at the 
same time allow the zinc vapors to oxidize the gases 
are run through an extended pipe. The pipes are made 
of sheet steel, and are 4 feet in diameter. Hach fur- 
nace block has considerable length of this pipe carrying 
the oxide stream and the intertwining arrangement of 
these large pipes, carrying the products of thirty-eight 





Fia. 29.—Down legs and drums. 


blocks in a row, presents a rare spectacle. At certain 
intervals, along the length of the pipe, are little doors 
called ventilators. ‘These ventilators permit the en- 
trance of air which cools the gas stream and aids in the 
oxidation or any remaining zine vapors. 

Sediment forms in the pipes and at sections near the 
furnace building, where high temperatures are encoun- 
tered, there may be semi-metallic deposits. This sedi- 
ment and these deposits ave very detrimental to the 


AMERICAN PROCESS ZINC OXIDE 67 


main product, zine oxide. Thus the pipes must be 
thoroughly cleaned periodically. This is done by cool- 
ing the furnace and sending men into the pipes to chisel 
loose and scrape away the accumulated sediment. 
This is done by picks, bar scrapers and special tools. 
The sediment, consisting of caked zinc oxide and 





Fia. 30.—View of zine oxide pipes carrying the zinc oxide laden gases 
from the furnace building. 


metallic zine, can be re-fed to the furnace and the zine 
content reworked. 

The drawing off of the oxide stream, as it forms in 
the furnace, and the propulsion of the gases and the 
pigment through the drums and the pipes is accom- 
plished by means of a large fan. The large cooling 
pipes lead the zinc oxide streams to fans. The fans 


68 ZINC OXIDE 


are set in special fan houses located midway between 
the furnace buildings and the bag houses. ‘The fans 
are of the centrifugal type, having closed gas inlets at 
both ends of the revolving axis. ‘The fins of the fan 
blow the zine oxide laden gases off through a tangent 
lead off pipe, through which it is led from the building. 
The fans are driven by electric motors and revolve at a _ 
speed of 350 to 400 r.p.m. ‘They are mounted on a 
special water-cooled roller bearing as the temperature 
of the gases is so high that special care must be taken 
of the bearing surfaces. Each fan has several openings 
which permit periodical cleaning of any accumulations 
of zinc oxide, dirt, etc. 

The zine oxide stream is then led, by means of large 
sheet steel piping, to a cyclone blower. ‘The cyclone 
blower is a mixing chamber where the dust particles of 
the oxide stream are blown in contact with vertical baffle 
plates, the forward motion temporarily arrested, and if 
too heavy for suspension in the moving gas stream, 
drop to the bottom of the cylindrical enclosure and from 
there down to the conical 
base of the cyclone blower 
where it is immune from the 
blast of the moving gases 
above. The cyclone blower 
is suspended on a structural 
steel base, with legs of suffi- 
cient height to be on a level 

Fie. 31.—Cyclone blower. —_ with the pipes carrying the 

oxide streams. The conical 
collection section in the base is far enough above the 
ground level to permit a small railroad truck car to 
go beneath it for the removal of collected refuse. 





eis 
SI 


AMERICAN PROCESS ZINC OXIDE 69 


The oxide stream is led off from the top center of the 
cyclone blower and is forced through a sheet-steel pipe 
to the bag house. There are two large bag houses at 
this plant the only difference being that at the one bag 
house the oxide stream is fed to the bottom of the bags 
and in the other it is fed at the top. 

The main pipe leads the oxide stream into the top of 
the building and there feeds it to a large lateral pipe. 
This lateral pipe runs at right angles to the main incom- 
ing pipe and extends along the side of the building. It 
feeds ten sub-pipes, five on each side of the main 
incoming pipe. These sub-pipes carry the oxide 
stream across the width of the building. Each sub- 
pipe feeds nineteen circular openings to which are 
attached collection bags. 

The bags are made of mesh muslin sheeting or tubing, 
so sewed as to become a tube 20 inches in diameter. 
The bags hang to a total length of 42 feet, being made 
of three sections of 14 feet each. They are made in 
sections so that if one part becomes defective it will 
not be necessary to replace the entire bag. The oxide 
laden gases enter the bag at the top and as they pro- 
ceed downward the gases escape through the meshes 
of the bags but leave behind the solid particles of zinc 
oxide. The gases entering the bags are very hot, 
and if for some irregularity they are not sufficiently 
cooled they may cause the bags to ignite and result in 
a very destructive fire. As the gas stream comes into 
' the building it is about 197° C., at the top of the bag 
it is about 168° C., half way down the bag the tempera- 
ture has dropped to 77° C. and at the bottom of the 
bag the temperature will have dropped to 49° C. 

The zinc oxide collects at the sides of the bags and 


70 ZINC OXIDE 


adheres to the cloth. As the bags get coated with zinc 
oxide there is a tendency to seal over the interstices 
of the meshes of the muslin and it is necessary to clean 
the bags of this accumulated zinc oxide so as to permit 
the escape of incoming gases. This cleaning is done 
by hand. By closing a damper each bag can be cut off 
from the incoming gases, and this also releases the pres- 
sure which usually holds the bags well extended. While 





Fig. 3la.—View of zinc oxide plant. Showing pipes, cyclone and bag 
house. 


they are cut off from the incoming gases, and hence 
hanging slack, a workman grabs hold of the side and 
by quick snappy shaking loosens the oxide which falls - 
to the bottom hopper and into the collection bags at 
the floor level. The gas is then admitted to this bag 
and another one shut off and shaken. In this way the 
bags are kept clean on the inside and the pigment is 
collected into the small collection bags on the ground 
floor of the bag house. 

When the collection bags at the bottom hoppers are 
sufficiently filled with zine oxide they are removed, 


AMERICAN PROCESS ZINC OXIDE fel 


tied shut by means of special colored strings, which 
mark the contents, and loaded on a small truck. 
Samples are taken so that by the time the pigment is 
ready to be packed it will have been classified and 
graded and will be used accordingly. A small electric 
truck makes up a train of the collection bag trucks 
and hauls them to the lower floor of the packing house. 
Here the bags are weighed, recorded and after labeling 
are allotted to the mixing room. After the destination 
of a lot is decided upon it is placed on an elevator and 
taken to the fourth floor of the building and placed 
at the side of the mixing hopper into which it is to go. 

Each collection of zine oxide at the bag house varies 
as to the time and the bag through which it is collected 
and this variation is sufficient to make some mixing 
necessary for the marketing of a standard product. 
The samples taken from the collection bags are taken to a 
testing room where they are rubbed down in oil, com- 
pared, graded for color and brightness and allotted for 
the mixtures. Thus the pigments are blended and a 
standard uniform product is procured. 

From the wide shelf-like hoppers on the fourth floor 
the mixed zinc oxide falls into the bolting machines 
which are on the third floor. These are special zine 
oxide bolting machines, fashioned after the flour bolting 
machines, having the zinc oxide led into the center 
of a revolving-screen cylinder, which is made of 16-20 
mesh brass wire. The oxide is put through these 
screens not, as some people think, to regulate its fine- 
ness, but to pick out any pieces of foreign matter which 
might have gotten into it, such as pieces of bag, bag 
string, etc. As the pigment passes directly from the 
bolter to the packer it is essential that all foreign matter 
be removed at this point. Beside functioning as a 


72 ZINC OXIDE 


cleaning medium for the zinc oxide the bolter also 
acts aS a mixing agent, mixing the zinc oxide to an 
even composition. 

















































































































eee ee 





Heh QD 
SESH is 


AY PS 
Trp Ih CHB 
ai SHY ee 

Say i ; 





Fig. 32a. 


Fia. 32 and 32a.—Cross and end sections of bolting machine. 


AMERICAN PROCESS ZINC OXIDE vo 


The zinc oxide then drops to the hopper of the packing 
machine located on the floor below. The packing 
machine is the flour packing type, having a large feeding 
tube which leads the zine oxide into a bag or barrel. 
Within this tube is an auger which rotates and forces 
the pigment down into the bag or barrel. The bag or 
barrel to be filled is placed on a counterweighted plat- 
form which is lifted so that the pigment feeds directly 





(Courtesy of Barnard & Leas Mfg. Co.) 
Fia. 32b.—Zinc oxide bolting machine. 


to the bottom of the container. As the filling pro- 
ceeds the platform is forced downwards and after it 
drops a given set distance it traps itself and throws 
the packing machine out of gear. The machine is 
adjusted so that it usually fills a given amount of pig- 
ment into a bag or barrel. The bags or barrels are 
removed from the packing machine platform and are 
weighed, more pigment added if necessary or some 
removed, so that the weight of the package is standard 


74. ZINC OXIDE 


at all times. The packages are tied, barrels headed 
and labeled on the packing floor, later to be trucked 
to a storage house from where they are shipped. 

Zinc oxides made by the Eastern Type of American 
Process furnaces are principally the so-called lead free 





(Courtesy of S. Howes Mfg. Co.) 
Fig. 33.—Zine oxide packing machine. 


grades of the pigment. Low leaded and high leaded 
zinc oxides are also made. Lead-free zine oxide is 
used in the rubber industry as a compounding pig- 
ment and in the paint industry as a pigment for use in 
conjunction with lead and other pigments. 


AMERICAN PROCESS ZINC OXIDE Pes; 


Considerable time and money is being spent for 
researches into a means for producing American Process 
zinc oxide by better methods. The most notable devel- 
opment that so far has been made public was the work 
on a continuous furnace developed by means of the 
traveling grate. Briquetted coal is charged mechan- 
ically to a depth of 6 inches at the one end, it is ignited 
by the radiated heat of the furnace walls, and burned 
by an under-grate blast, and has an arrangement for 
carrying off the issuing gases. In this combustion 
chamber the temperature rises to about 800° C. to 
850° C. As it travels along it forms the bed coal 
and underlies a briquetted ore charge fed continuously 
to a 3-inch depth. ‘The charge, ignited by the bed 
coal, gives off gases which are carried off through a flue. 
In this second section the temperatures rises to about 
1000° C. By the time the charge has been heated to a 
temperature for reducing the zinc contained in the ore © 
charge the traveling grate has carried it to a separate 
chamber about 18 feet long. The under grate blast fur- 
nishes continuous air for the oxidation. ‘The tempera- 
ture of the main reducing chamber is about 1100° C. 
to 1250° C. The treated ore briquettes retaining their 
shape pass off at the tail end of the grate into a hopper 
where part of the fuel ash is screened off. The grate 
travels at a speed of 7 feet a minute. ‘The use of ore- 
fuel briquettes has given hopes of reducing the amount 
of fuel necessary for a charge, and has given a greater 
percentage of recovery of the total zinc content. 

A novel variation of the general design of the Amer- 
ican Process furnaces and plants is found in a zine oxide 
plant in Illinois. The raw material charge, composed 
of both the fuel and the ore, is raised to a storage bin 


76 


ZINC OXIDE 
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Fic. 34.—New traveling grate zinc oxide furnace. 


AMERICAN PROCESS ZINC OXIDE fire 


by means of a bucket elevator. From this bin it is 
tapped directly into the buckets of a chain bucket 
trip conveyor. The conveyor takes the charging 
material out over the center of the block and by means 
of regulated trips dumps the contents into furnace bins 
which are below the conveyor and are directly above 


L/ K—% 


LLLL LA XK 





WA 


/ 
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Fig. 35.—Novel American Process zinc oxide furnace. 


the furnace block. This conveyor goes on down to 
the end of the building and returns beneath the furnace 
block carrying away the clinker from the collection 
hopper beneath the furnace floor. 

The furnace used in this plant is of a four-furnace 
block type. It has the charge neck and the gas port 
combined in one furnace opening and thus only has the 


78 ZINC OXIDE 


one opening into the arch of the furnace roof. A 
counterbalanced raising door is used instead of the 
banked ash door. The clinker and ashes are removed 
by allowing them to fall through an open floor door, 
and into a bin, at the base of which runs the chain 
bucket conveyor. 

The zinc oxide formed leaves the furnace through the 
charge opening, and goes to the down leg through a 
butterfly valve. The actual charge opening is covered 
over as soon as the charge has been dropped into the 
furnace. ‘The down leg leads the zinc oxide into a side 
drum, there being a drum for each furnace of the block. 
From the side drums the gas stream is led to a top drum 
where the mixing of the entire stream of zinc oxide is 
effected. 

The cooling pipes, with cooling ports every 10 feet, 
and fans are the same as previously described but the 
bag house and the system of collecting the zine oxide 
differs in several respects. 

The bag house is really an elevated building with 
a sheet metal hopper bottom. The stream of zinc 
oxide laden gases enter the side of the hopper and 
rises through a series of outlets which feed upward 
into bags. The bags are 10 inches in diameter and 
15 feet long. ‘They are mechanically shaken every 10 
minutes by a cam and gear arrangement actuated 
by a revolving center rod. The shaking is timed 
by means of a cam gear arrangement on the fans. 
The shaking is effected by a solenoid causing the cams 
to come in contact with suspending arms of the bags 
and giving the bags an up and down jerky motion, and 
at the same time causing two metal rods which run 
along the side of the bag to slap up against it and thus 


AMERICAN PROCESS ZINC OXIDE 79 


loosen all of the zinc oxide settled on the interior of the 
bag. 

The zinc oxide falls into the large hopper below, which 
is V-shaped, and extends the width of the building. 
The zinc oxide is propelled along the base of the hopper 





Fig. 36.—Novel bag house of an Illinois zine oxide plant. 


by means of a hand-operated screw propeller and at a 
central point it is tapped into small trucks. These col- 
lection trucks have an upright barrel-like body which 
may be covered at the top to keep the zinc oxide clean, 
and may easily be emptied by opening the gate at the 
bottom. The workmen very appropriately call the 
trucks ‘‘ torpedoes.”’ 


CHAPTER 7 


AMERICAN PROCESS ZINC OXIDE 


Western Practice 


The Western practice of producing zinc oxide by the 
American Process differs from the Easter practice prin- 
cipally in the furnace construction and operation. 

The furnace block of a western type furnace is com- 
posed of usually eight to sixteen full width or “‘ double ”’ 
furnaces placed side by side, none of which have arches 
but are so constructed that all gases and fumes flow 
to a common arched roof. The furnaces have the air 
duct, water seal, ash pit, use the Wetherill pin-hole 
grates, and maintain a furnace temperature of about 
1000° C. to 1100° C. , 

The operation of the furnace is by hand. The fuel 
charge is shoveled into the furnace from both sides, 
counterbalanced doors being used. When the fuel burns 
freely, being ignited by the residual heat from the previ- 
ous charge, the ore charge of zinc ore and coal (usually 
half as much coal as ore) is shoveled into the furnace and 
spread to a thickness of 6 to 8 inches, and the cold blast 
slowly turned on. The furnace does not require any 
special attention for several hours, except that the 
charge be watched for blow-holes. After about six 
hours the charge is rabbled and in one hour later it is 

80 


AMERICAN PROCESS ZINC OXIDE 81 


rabbled again. ‘The charge is reduced in eight hours 
and is then drawn. 

The zinc fumes, the gases of combustion and the 
zinc oxide formed in the furnace rise to the arched roof 
of the block. All of the furnaces feed to the common 
arch, each furnace really being a partition of a large 
furnace block. From the furnace block the gases are 
led to the combustion chamber. The combustion 
chamber is a large firebrick chamber, the purpose of 
which is to thoroughly intermix all the zinc oxide com- 
ing from the furnace and to allow oxidation of any zinc 
vapor that remains. ‘The combustion chamber, having 
an excess of free sulphur gases present, will cause lead 
oxide formed in the furnace to be converted into basic 
lead sulphate, which is white and accordingly does 
not have a tendency to discolor the pigment as would 
lead oxide. It also acts as a settling agent and any 
heavy particles are settled out in this chamber. 

The cooling of the zinc oxide stream is effected by 
large pipes, the same as in the Eastern practice, and 
the zinc oxide collected in bags of the same design. 

The Western furnaces use principally roasted blende 
and oxide ores, and as fuel they use a semi-bituminous 
coal, although several plants now in operation use coke 
breeze and anthracite coal. as fuel. The principal 
products of the Western furnaces are leaded zinc oxides. 
Temperatures are relatively constant and by uniform 
procedure a high quality uniform leaded zinc oxide 
can be produced. 

One of the most recently constructed Western 
practice American Process plants is at Murray, Utah, 
and is owned by the Utah Zinc Company. 

The zinc ore used at this plant is a low lead content, 


82 ZINC OXIDE 


20 per cent zinc ore, mined in Utah. The ore is brought 
to the plant by rail and dumped from the cars on a 
trestle and allowed to weather without rehandling. 
It is later placed on a 20-inch belt conveyor which car- 
ries it to the crushing plant. 

The crushing plant is designed to handle 150 tons of ore 
each eight-hour shift. The ore is passed over a ?-inch 
grizzly and thence to a 10-inch by 20-inch Allis Chal- 














Fig. 37.—Zine plant at Murray, Utah. 


mers Blake crusher. The crushed ore is elevated by 
means of a bucket elevator to a ¢ inch square mesh 
trommel, the oversize from which falls into a set of 
14-inch by 30-inch rolls and from the rolls to the foot of 
the elevator. The crushed ore that passes the trommel 
goes directly to a large crushed ore storage bin capable 
of holding about 350 tons of crushed ores. The differ- 
ent ores going into the storage bin are distributed by 
means of an 18-inch belt conveyor which in turn feeds 
it to shuttle conveyors. 


AMERICAN PROCESS ZINC OXIDE 83 


The ore is drawn from the storage bin into small 
trucks, weighed and dumped into a large concrete 
mixer. Coke breeze is also drawn from a storage bin, 
weighed and dumped into the mixer. Water sufficient 
to give proper moisture content is also placed in the 
mixer and the charge is given five minutes’ churning. 

The mixed ore and coke is elevated by means of a 
second 60-foot bucket elevator to the mixed ore bin. 
The bin is designed to store 150 tons of mixed ore. A 
portion of this bin is also used for coke storage—the 
fuel charge of the furnace. 

The fuel charge of coke and the burden charge of 
mixed ore and coke are drawn from the storage bin 
into the charge cars that are low and wide, and which 
are so designed with hinged lip that the side can be 
turned down to form a shelf flush with the bottom. 
These cars are run up alongside the furnace and the con- 
tents shoveled into the furnace doors in charging the 

individual sections. 
~The furnace building is constructed of concrete and 
structural steel, having its roof and sides made of cor- 
rugated iron. ‘The foundations are all concrete and 
support the furnace and operating floor, which is also 
concrete and is elevated 7 feet 3 inches above the 
ground level. 

The furnace consists of two volatilizing sections flank- 
ing a central section, which is the combustion chamber. 
The furnace is so designed that either section can be 
cut off from the combustion chamber if it is so desired. 
There are sixteen hearths in the furnace, eight in each 
section. ‘The concrete foundation beneath each sec- 
tion forms individual chambers 9 feet 2 inches deep 
and 6 feet 6 inches by 13 feet in area. These enclosed 


84. ZINC OXIDE 


chambers are filled with water and serve the purpose of 
cooling the grates, and thus preventing buckling, and 
for collecting any ashes that may pass through the 
Wetherill grates. The water for the chambers is sup- 
plied through a 32-inch feed pipe controlled by a valve ~ 
operated from the charging floor. An overflow is 
provided immediately below the blast inlet and 14 
inches below the grates. A water-tight door near the 
bottom of the chamber can be removed to clean out 
the accumulation of ashes which in time may become 
troublesome. 


ini 
ss as 
SIS SS AASSASASSASAY 
a SALTS 


RABBROAHE AES EES 






\! 

iH ; f 
(Yi! | 
anaiin 


(LEY 


ies fo ‘ 
< }-————— ’ ~ . 
> . 
Ny S , .? " 
5 . 
‘ 
: “N = }. 
5 SN oe . 
: ‘ - S 
a O “LO Te 
TN eS . A = 
. = ae . . . 
eS? SS Us 3 SAAD suk ST SL Peas Syaph a ew 


Fic. 38.—Western type of zinc oxide furnace. 


The grates of the furnace rest on I beams supported 
by the concrete. An 8-inch blast pipe enters each 
chamber just below the grate level. The furnace is 
constructed of common brick, lined on the inside by 
firebrick. ‘The top of the main arch is 8 feet 6 inches 
above the top of the grates while the smaller arches are 
40 inches high and extend 33 feet into the furnace. 
The furnace is substantially built and is reinforced by 
brick, stays of channel and I beams and #-inch rods. 
A firing or feeding door is provided for each of the 
short arches, making sixteen doors for each section of 
the furnace. 


AMERICAN PROCESS ZINC OXIDE 85 


The earlier designs of the Western type furnaces 
had doors along one side of the furnace only, rather than 
the two rows of doors opposite each other. The later 
design of doors on both sides of the furnace has a dis- 
advantage in that it permits the furnace to cool rapidly 
during cleaning and charging periods, but this is pos- 
sibly offset by the facility with which accretions can be 
removed and the ease with which recharging can be 
done. ‘The furnace not having a back wall, permits the 
side walls to be cleaned easily and allows for more 
rapid cleaning of the grates. 

The grates are of the Wetherill type, similar to those 
used in all American Process zinc oxide furnaces. They 
are cast iron with tapering perforations § inch in diam- 
eter at the top surface and are spaced 1 inch in both 
directions. The combustion chamber is a large brick 
chamber connected on either side by brick passages, or 
‘‘ bridges ”’ to the furnace sections where the zinc oxide 
is volatilized. In the sides of these passages, or bridges, 
are small arched openings, like windows. These win- 
dows are checkered with brick masonry and removable 
bricks are provided to allow the regulation and flow of 
fresh air into the combustion chamber. 

Once the furnace is in operation the procedure con- 
sists of drawing and recharging in rotation the indi- 
vidual doors of the furnace hearths. The procedure 
is as follows: The blast is cut off from the particular 
furnace section to be cleaned and the furnace is opened. 
The loose part of the last charge is raked off by hand 
and deposited on the floor to be used for recharging 
later. ‘The semi-fused clinker is removed in a fashion 
similar to the cleaning of fires under a coal-fired boiler, 
a slice bar being used to break it up and a rake used to 


86 ZINC OXIDE 


draw it from the furnace. The clinker is dropped 
through a hole in the floor directly in front of the 
furnace door, to a car beneath in which it is transported 
to a dump. A layer of freshly moistened coke breeze 
is shoveled into the furnace and spread to an even 
depth on the cleaned grate. The blast gate is partly 
opened to admit air. The residual heat from the hot 
brickwork of the arch ignites the fuel and when it is 
burning briskly the material saved from the prior fur- 
nace charge, with a quantity of ore and coke mixture 
from the recharge car is shoveled into the furnace and 
spread evenly over the bed of fuel. The furnace door 
is then closed and the full blast turned on. ‘This 
completes the charging and the furnace men then fro- 
ceed to repeat the operation in the next furnace division, 
and so continue around the furnace working the six- 
teen divisions in succession. In the presence of carbon 
in the form of coke the zinc of the ore is first reduced 
and volatilized; it is then oxidized by coming in con- 
tact with an excess of air in the large arch and in the 
combustion chamber. A brick down-take conveys the 
fume-laden gas to a rectangular cooling flue which is 
also made of brick. 

The air pressure in the blast beneath the furnace 
grates 1s equivalent to 4 inches of water. ‘This blast is 
supplied by a Sturtevant multivane fan of a capacity 
of 40,000 cubic feet per minute at a speed of 460 r.p.m. 

From the combustion chamber down-take the zinc 
oxide laden gas is drawn into a cooling flue. The 
cooling flue is a circular sheet iron pipe 45 inches in 
diameter and 1000 feet long. It is supported by low 
bouts about 5 feet above the ground. A shorter flue is 
undesirable because it does not give the gases suf- 


AMERICAN PROCESS ZINC OXIDE 87 


ficient time to cool. Elbows and sharp turns are 
avoided because they offer unnecessary resistance to 
the flow of gas. Expansion joints are provided every 
30 feet while at intervals of 8 feet along the bottom of 
the pipe are small openings fitted with sliding gates. 
Through these gates any oxide that settles may be 
withdrawn when necessary. The draft, however, is 
such that this accumulation does not amount to much. 

The flow of zinc-laden gas through the cooling flue is 
effected by a 140-inch Sturtevant exhaust fan situ- 





Fig. 39.—Combustion chamber and down-take. 


ated at the end of the flue near the bag house. The 
fan has a capacity of 70,000 cubic feet per minute at 
300 r.p.m. and creates 1; ounces per square foot 
in effluent gas. The high temperature of the gases 
make it necessary to have the bearings on the fan water 
cooled. 

The bag house, in which the zinc oxide is collected, 
is 100 feet by 70 feet and has a wall 22 feet high. The 
zinc-laden gases enter at the bottom of the building and 
are distributed through the main pipes and laterals to 
528 seamless cotton bags. The bags are 22 inches in 
diameter and are 28 feet high. The lower and open 


88 ZINC OXIDE 


ends of the bags fit snugly around the collars on the dis- 
tributing pipes while the upper ends of the bags are 
closed and are supported by short ropes or small chains 
suspended from the grillwork below the trusses of the 
roof. ‘The meshes of the bags collect the zine oxide 
and allow the gases to escape. 

The zinc oxide is shaken loose from the bags and is 
collected in bags attached to the under surface of the 
distributing pipes. When these collection bags are full 
they are detached and the contents hauled to a 9-inch 
extra heavy screw conveyor which carries the oxide 
horizontally 70 feet to the building where the packing 
is done. Here it is elevated by means of an 8-inch 
bucket elevator to a small storage bin from which it is 
drawn for packing. 


CHAPTER 8 


SPECIFICATIONS FOR THE PHYSICAL AND CHEMICAL 
QUALITIES OF ZINC OXIDES 
STANDARD METHOD OF SAMPLING ZINC OXIDE 
Product: U. S. Pharmaceutical Zinc Oxide. 
The physical properties of this product must con- 


form to standard samples when compared by the 
methods specified. 


Physical 
Test Number 
a ated oa whe Ss 1 
COSTES A eet i 2 
Smoothness and freedom from specks.. 3 
MOC NET tae ee ek sos ea 4 
epee ALGIy Ge... Safe eas ss owes 5 


The Chemical Properties —The chemical constituents 
of this product, as listed below, must be within the 
limits indicated when tested by the standard method 
of analysis specified. 


Limits Analysis 

Per cent Number 
Insoluble in‘ HCl....... 0O- .010 4. 
Peal tO? Ge... y 0O- .150 3 
BOabotal S:as)........ 0O- .060 5 
H20 soluble salts...... 0O- .200 2 
Cle UU 0O- .020 1 
PbsO, (total Pb as).... 0O- .040 9 
ee hee a oe us 0O- .005 39 
TDD Ua 8 99 .0—-100.0 10 
LCOS Sa iC ser IR ns a ge 15 
Maralenedyry Metals. =... o celts vints'e 12 


90) ZINC OXIDE 


Product: French Process Zinc Oxide. 


The physical properties of this product must conform 
to standard samples when compared by the methods 
specified. } 


Physical 
Test Number 
Color. 06 seins 6 cs ee | 
Brightness... 0. sls 2 
Smoothness and freedom from specks.. 3 
Hiding power. .. ... 20.0 0ie 
Settling in water..... 2... 2. 5 


The Chemical Properties.—The chemical constituents 
of this product, as listed below, must be within the 
limits indicated when tested by the standard method of 
analysis specified. 


Limits Analysis 

Per cent Number 
Insoluble in - HCl = 3 ree 0.0.03 4. 
H3O st110°% Co eee 0-0.25 3 
SOs (total Sas) an eee 0-0.25 5 
H30 soluble salts: oe 0-0.75 2 
Cate LEC a Sees eee 0-0 .06 1 
PbSOw (otal Phas) 2 eee 0-0.55 Zor8 


QUALITIES OF ZINC OXIDES 9] 


Product: Lead Free Zinc Oxide for Rubber Compounding. 


The physical properties of this product must con- 
form to standard samples when compared by the 
methods specified. 


Physical 
Test Number 
A ehh a va ed hae 1 
Smoothness and freedom from specks.. 3 
MIRO WET fee. Sieg bs vase py wale 8 


The Chemical Properties.—The chemical constituents 
of this product, as listed below, must be within the 
limits indicated when tested by the standard method 


of analysis specified. 
Limits Analysis 
Per cent Number 


Insoluble in acetic acid...... 0-0.25 16 
Sica Ne ey ea 3 OH eer 0-0.100 4 
eee eC co lees 0-0.40 3 
Ureuetal AS)... ek 0-1.00 5 
SOs (reducing power equiv.to) 0.20 13 
HeO soluble salts........... 0-1.50 2 
Oy, 0-0.10 1 


PbSOu (total Pbas)......... 0-0.40 7or8 


92 ZINC OXIDE 


Product: Superfine Rubber Makers, Zinc Oxide. 


The physical properties of this product must conform 
to standard samples when compared by the methods 
specified. 


Physical 
Test Number 
Particle size... .4.4):...) eee td 
Colori.s..00 0.6) Ae ee at 
Tensile strength and elongation...... 12 
Abrasion resistance... -...... 2s ars 
Rate of cure.. .-... ..4... 14 


The Chemical Properties —The chemical constituents 
of this product, as listed below, must be within the limits 
indicated when tested by standard method of analysis 


specified. 
Limits Analysis 
Per cent Number 


BO 10a ae ee ae 0.00-0.75 3 
Insoluble in acetic acid.. 0.00-0.15 14 
PbO. (total: Pb -as\ysen= = 0.10-0.25 8 


QUALITIES OF ZINC OXIDES 93 


Product: Lead Free Zinc Oxide for Paint Manufacturing. 


The physical properties of this product must conform 
to standard samples when compared by the methods 
specified. 


Physical 
Test Number 
OT ke wie ep Sie a kas 1 
Re as 4 nfs gov aus ws mle ds 2 
Smoothness and freedom from specks.. 3 
PIPER DOOWCT) oo. cies oe ce fale ewe ws oe 4 
Ou LOTS Ta A a 6 


The Chemical Properties.—The chemical constituents 
of this product, as listed below, must be within the 
limits indicated when tested by standard method of 
analysis specified. 


Limits Analysis 

Per cent Number 
Preaiinemm HOl. ......... 0-0.040 4. 
(ni) )2re 2 0 eG iS 0-0.40 a 
BO potslO 8S).......,.< 0-0.45 5 
SOz (red power equiv. to).. 0—-0.20 13 
Pi eeOeSallS tis ob wee 0-1.25 2 
Old Se 0-0.10 1 


PbSOz (otal Pb as)....... 0-0.82 Zors 


94 ZINC OXIDE 


Product: Five Per Cent (5%) Leaded Zinc Oxide. 


The physical properties of this product must conform 
to standard samples when compared by the methods 
specified. 


Physical 
Test Number 
Color.y.. 0s 1 
Brightness. .....+)3.5.5 so 2 
Smoothness and freedom from specks.. 3 
Hiding power. «i 3... 2.4.05 ee: 
Tail length: ; ... 2.05; «2. 9 6 


The Chemical Properties —The chemical constituents 
of this product, as listed below, must be within the 
limits indicated when tested by standard method of 
~ analysis specified. 


Limits Analysis 

Per cent Number 
Insoluble in HCl........ 0-0.15 4. 
HsOwtiloY Cee 0-0 .40 Fe 
Total SOsdmin ja aes 0-0.70 9) 
SOs (red. power equiv. to) 0-0.30 13 
HsO soluble salts eae. = 0-1.25 2 


PbSOs, (total Phas)..... 3.0-5.5 6 or 7 


QUALITIES OF ZINC OXIDES 


95 


Product: Thirty-five Per Cent (35%) Leaded Zinc Oxide. 


The physical properties of this product must conform 
to standard samples when compared by the methods 


specified. 
Physical 
Test Number 
CTE ES ce eee 1 
U2 SN Z 
Smoothness and freedom from specks.. 3 
ee ONO. ies ler sk es 4 
(LU LOE fo Sa ae 6 


The Chemical Properties.—The chemical constituents 
of this product, as listed below, must be within the 
limits indicated when tested by standard method of 


analysis specified. 


Limits 

7 Per cent 
Insoluble in HCl........ 0— 0.30 
eae Ae 0- 0.40 
Ota OO. tMin.)).. 2... . 5. 50 
SOz (red. power equiv. to) 0-0.70 
He solsalts.........:. 0-1 .20 


PbsO. (total Pb as)..... 33.0-37.0 


Analysis 
Number 


4 
3 
15 
13 
2 
6 or 7 


96 ZINC OXIDE 


STANDARD METHOD OF SAMPLING ZINC OXIDE 


Shipping, receiving or arbitration samples from pack- 
ages that have been closed shall be taken with a long, 
narrow sampling scoop, approximately 25 inches long, 
the section being an are approximately 1 inch across 
and 2 inch deep. ‘This scoop shall be inserted at the 
top of the barrel at a point not more than 6 inches from 
the chime, or through a stave within 12 inches of the 
one end, and thrust obliquely through the contents of 
the barrel. The sample thus cut out shall be of length 
equal to at least half the height of the package. 

In taking samples from bags, the scoop shall be 
inserted near the edge of the surface of the contents, 
and thrust obliquely through the material. The sam- 
ples thus cut shall be of length equal to at least two- 
thirds the height of the package. 

If a moisture determination is to be made, at least 
half a pound sample shall be taken, as above described, 
and immediately placed in an air-tight receptacle, 
which it must fill. 


CHAPTER 9 


STANDARD METHOD OF TESTING THE PHYSICAL QUALITIES 
OF ZINC OXIDE 


PuysicaL Testing Mrtuop NuMBER ONE 
For THE PROPERTY OF:—COLOR. 


Description: 

Approximately 5 grams of the sample shall be thor- 
oughly mixed with the smallest quantity of bleached 
linseed oil that will produce a smooth paste. This 
paste shall be spread on a palette of colorless plate-glass 
in a smooth and even layer, that will not transmit 
light and is at least 1 inch by 3 inches in area. 

An equal amount of the standard sample shall be 
prepared in the same way, care being taken to bring 
the paste to the same consistency as the sample being 
tested. This paste shall be spread in a similar manner 
on the palette beside the sample, touching it, and the 
two compared in diffused daylight. In doing so, the 
palette shall be tilted so that the light will strike the 
surface of the pastes at different angles and the under 
surfaces shall also be observed through the glass. 

In doubtful cases only the sample and one standard 
sample may be spread on the palette at the same time, 
and their edges must touch. 

To be on-grade the sample must be as white as the 
standard. 

4 


98 ZINC OXIDE 


PuysicaAL Trstinc Mrtuop NuMBER Two 
For THE PROPERTY OF:—BRIGHTNESS. 


Description: 


Five grams of the sample and 1.20 grams of bleached 
linseed oil shall be mixed to a smooth, uniform paste. 
The oil used may be determined by dropping from a 
point which has been standardized by counting the 
number of drops necessary to weigh 1.20 grams. The 
dropping shall be at a rate not greater than 70 drops 
per minute. All the sample and all the oil must be 
thoroughly incorporated. This paste shall be spread 
on a palette of colorless plate-glass in a smooth and 
even layer that will not transmit light and is at least 
1 inch by 3 inches in area. ; 

When the nature of the pigment requires more oil 
than above noted, more shall be used but comparisons 
shall be made only between samples which have a like 
oil-vehicle ratio. | 

An equal amount of the standard shall be prepared 
in the same way. ‘This paste shall be spread in a sim- — 
ilar manner on the palette beside the sample, touching 
it, and the two compared by observing in diffused day- 
light the two samples by looking through the glass. 

In doubtful cases only the sample and one standard 
may be spread on the palette at the same time, and 
their edges must touch. 

To be on-grade the sample must be equal to or better 
than the standard in brightness or brilliancy. 


TESTING THE PHYSICAL QUALITIES OF ZINC OXIDE 99 


PuysicaL Testing Mretuop NuMBER THREE 
For THE PROPERTY OF:—SMOOTHNESS AND 
FREEDOM FROM SPECKS. 


Description: 


Approximately 5 grams of the sample shall be thor- 
oughly mixed with the smallest quantity of bleached 
linseed oil that will produce a smooth paste. This 
paste shall be spread on a palette of colorless plate-glass 
in a smooth and even layer that will not transmit light 
and is at least 1 inch by 38 inches in area. 

An equal amount of the standard shall be prepared 
in the same way, care being taken to bring the paste 
to the same consistency as the sample being tested. 
This paste shall be spread in a similar manner on the 
palette beside the sample, touching it, and the two 
compared in diffused daylight. In doing so, the palette 
shall be tilted so that the light will strike the surface 
_ of the pastes at different angles. 

In doubtful cases, only the sample and the one stand- 
ard may be spread on the palette at the same time, and 
their edges must touch. 

To be on-grade the sample must contain no more 
granular or foreign matter than the standard. ‘This 
is to be determined by the feel under the knife and the 
amount of noise made in the rubbing down and by 
observation of the surfaces after the pastes have been 
spread on the palette. 


100 ZINC OXIDE 


PuysicaL TEstTiIncG MretHop NuMBER FouR 
For THE PROPERTY OF:—HIDING POWER. 


Description: 


Five grams of the sample, 0.5 gram of ultramarine 
blue and 1.20 grams of bleached linseed oil shall be 
mixed to a smooth uniform paste of uniform color 
throughout. The oil used may be determined by 
dropping from a point which has been standardized by 
counting the number of drops necessary to weigh 1.20 
grams. ‘The dropping shall be at a rate not greater 
than 70 drops per minute. The mixing shall be done 
by rubbing lightly with a spatula the blade of which is 
not over 5 inches long. All the sample, blue and oil 
must be thoroughly incorporated. This paste shall be 
spread on a palette of colorless plate-glass in a layer 
that will not transmit light. 

The standard shall be prepared in the same way and 
spread in a similar manner on the palette beside the 
sample, touching it. 

Another standard paste shall be prepared by mixing 
5.5 grams of the standard, 0.5 gram of ultramarine 
blue and 1.82 grams of bleached linseed oil in the same 
way and spread in a similar manner on the palette 
beside the sample, touching it. 

In doubtful cases, only the sample and the two 
standards may be spread on the palette at the same 
time and the sample must be in contact with both 
standards at the edges. 

To be on-grade the sample must not be darker than 
the first standard and not lighter than the second 
standard when observed through the glass. 


TESTING THE PHYSICAL QUALITIES OF ZINC OXIDE 101 


Puysicau TESTING MrtHop NuMBER FIVE 
For THE PROPERTY OF:—SETTLING IN WATER. 


Description: 

This test shall be made in a flat-bottomed glass tube 
of 41 inch diameter, 6 inches in height and uniform bore. 
Twenty-seven c.c. of water should fill it to a height of 
4# inches with an allowance plus and minus variation of 
zs inch. 

Five grams of the sample shall be put into the tube 
after the latter is half filled with water. ‘The product 
and water shall be well mixed with a piece of wire about 
14 or 12 gauge and the tube filled with water to a height 
of 4% inches. ‘The wire is to be removed and washed 
off in the process of adding this water. The tube 
shall then be shaken vigorously eighty times, the thumb 
being held over the opening at the top. After shaking, 
it shall be placed in a rack so that it stands vertically 
and the height of the column of the product measured 
at the end of 1, 2, 3 and 24 hours. 

An equal amount of the standard shall be treated 
in the same way. 

To be on-grade the height of the column of the sample 
must be within 10 per cent plus or minus of the height 
of the column of the standard at the end of 24 hours. 


102 ZINC OXIDE 


PuysicaL Testing Mreruop NUMBER SIx 
For THE PROPERTY OF:—TAIL-LENGTH. 


Description: 


A sample of 400 grams is mixed and ground in mills 
with 120 c.c. of refined linseed oil having an acid number 
of not less than 5 nor more than 7. This mix is by 
weight 78 per cent pigment and 22 per cent oil. After 
standing an hour or so, 40 grams of the paste shall be 
weighed out and thinned down to a mixture of 40 per 
cent pigment and 60 per cent oil. 

This mixture shall be stirred until the pigment is 
thoroughly incorporated in the oil to a uniform paint. 
Immediately after discontinuing the stirring a portion 
of the paint shall be drawn off into a glass pipette, 
having a ;;-inch orifice. The tip of the pipette shall be 
wiped off and the paint column is to stand in it at a 
height of 2 inches above the tip. Then holding the 
pipette vertically 4 inch above the clean, dry surface 
of a glass plate, 4 drops are allowed to fall on the plate. 
The latter shall immediately be placed in a vertical 
position and the paint allowed to run down it for exactly 
two minutes. 

A similar sample of the standard shall be treated in 
exactly the same way. 

To be on-grade the over-all tail-length of the sample 
must be within 20 per cent, plus or minus, of the over- 
all tail-length of the standard. 


TESTING THE PHYSICAL QUALITIES OF ZINC OXIDE 103 


PuysicaLt Testing Mretuop NumBer Eicut 
For THE PRopERTY OF:—HIpDING PoweEnr. 


Description: 

Five grams of the sample, 0.5 gram of ultramarine 
blue and 1.20 grams of bleached linseed oil shall be 
mixed to a smooth uniform paste of uniform color 
throughout. The oil used may be determined by 
dropping from a point which has been standardized 
by counting the number of drops necessary to weigh 
1.20 grams. ‘The dropping shall be at a rate not greater 
than 70 drops per minute. The mixing shall be done 
by rubbing lightly with a spatula the blade of which is 
not over 5 inches long. All the sample, blue and oil 
must be thoroughly incorporated. ‘This paste shall be 
spread on a palette of colorless plate-glass in a layer 
that will not transmit light. 

The standard shall be prepared in the same way and 
spread in a similar manner on the palette beside the 
sample, touching it. 

Another standard paste shall be prepared by mixing 
5.75 grams of the standard, 0.5 gram of ultramarine 
blue and 1.38 grams of bleached linseed oil in the same 
way and spread in a similar manner on the palette 
beside the sample, touching it. 

In doubtful cases, only the sample and the two 
standards may be spread on the palette at the same 
time and the sample must be in contact with both 
standards at the edges. 

To be on-grade the sample must not be darker than 
the first standard and not lighter than the second 
standard when observed through the glass. 


104. ZINC OXIDE 


PuysicaL Trsting Mrtuop NuMBER NINE 
For THE PROPERTY OF:—Or1L ABSORPTION. 


Description: 

The sample to be tested shall first be placed in a small 
wide-mouthed bottle and well shaken so as to eliminate 
any packed particles or lumps. 

Twenty grams of the pigment shall be weighed into a 
flat-bottomed glass. Refined linseed oil shall be added 
drop by drop from a burette. As the oil comes in con- 
tact with the pigment, the dry pigment which has not 
been wet should be lifted from the outer edge and placed 
over the oil so as to bring all the oil surface in contact 
with the pigment. This should be accomplished by 
lifting the pigment with a small spatula and lightly 
dumping it over the oil, at the same time giving the 
glass a circular motion and avoiding any pressure on the 
pigment. When the pigment particles become wet 
with oil, they tend to coalesce and form small lumps 
of paste. As the absorption of oil progresses these 
lumps of paste by taking up more pigment and matting 
together form larger lumps which when stirred around 
form balls. When this point is reached the rate and 
quantity of the oil addition shall be decreased until 
only a few drops of oil are added at a time. In adding 
oil at this point it should be allowed to strike on the 
lumps and not on the remaining dry pigment. After 
each oil addition these lumps are lightly stirred so as 
to bring the oil surface in contact with the remaining 
dry pigment. With the further addition of oil and 
further stirring, these balls will join together and form 
one large lump with but little dry pigment remaining. 
This point is close to the end point and the oil should be 


TESTING THE PHYSICAL QUALITIES OF ZINC OXIDE 105 


added very carefully, only one or two drops at a time. 
When the last of the dry pigment has been picked up 
and wet the end-point is reached. 

An equal amount of the standard shall be tested in 
the same manner, and under the same conditions, espe- 
cially temperature, care being taken to manipulate 
the test in the same manner, and to obtain a ball of the 
same consistency. | 

The number of cubic centimeters of oil required to 
reach the end-point is considered the oil absorption of 
the pigment. 

To be on-grade the sample must lie within a range 
the maximum of which is .30 c.c. more than the oil 
absorption of the standard sample and the minimum of 
which is .20 ¢c.c. less than the standard sample. 


106 ZINC OXIDE 


PuysicaL Testing Mreruop NUMBER TEN 
For THE PROPERTY OF:—Or1L ABSORPTION. 


Description: 

The sample to be tested shall first be placed in a 
small wide-mouthed bottle and well shaken so as to 
eliminate any packed particles or lumps. 

Twenty grams of the pigment shall be weighed into a 
flat-bottomed glass. Refined linseed oil shall be added 
drop by drop from a burette. As the oil comes in con- 
tact with the pigment, the dry pigment which has not 
been wet should be lifted from the outer edge and 
placed over the oil so as to bring all of the oil surface 
in contact with the pigment. ‘This should be accom- 
plished by lifting the pigment with a small spatula 
and lightly dumping it over the oil, at the same time 
giving the glass a circular motion and avoiding any 
pressure on the pigment. When the pigment particles 
become wet with oil, they tend to coalesce and form 
small lumps of paste. As the absorption of the oil 
progresses these lumps of paste by taking up more pig- 
ment and matting together form larger lumps which 
when stirred around form balls. When this point is 
reached the rate and quantity of the oil addition shall 
be decreased until only a few drops of oil are added at a 
time. In adding oil at this point it should be allowed 
to strike on the lumps and not on the remaining dry 
pigment. After each addition of oil these lumps are 
lightly stirred so as to bring the oil surface in contact 
with the remaining dry pigment. With the further 
addition of oil and further stirring, these balls will join 
together and form one large lump with but little dry 
pigment remaining. This point is close to the end- 


TESTING THE PHYSICAL QUALITIES OF ZINC OXIDE 107 


point and the oil should be added very carefully, only 
one or two drops at a time. When the last of the dry 
pigments has been picked up and wet the end-point is 
reached. 

An equal amount of the standard shall be tested in 
the same manner, and under the same conditions, espe- 
cially temperature, care being taken to manipulate the 
test in the same manner and to obtain a ball of the same 
consistency. 

The number of cubic centimeters of oil required to 
reach the end-point is considered the oil absorption of 
the pigment. 

To be on-grade the sample must lie within a range 
the maximum of which is .60 c.c. more than the oil 
absorption of the standard sample and the minimum of 
which is .10 c.c. more than the standard sample. 


108 ZINC OXIDE 


PuysicaL TEstTiInc MretHop NuMBER ELEVEN 
For THE PROPERTY OF:—COLOR IN RUBBER. 


Description: 
The sample shall be incorporated in a rubber com- 
pound of the following composition by weight: 


First latex pale crepe... eee 920 
UID HUT ee ae ‘eh sa 55 
Hexamethylenetetramine.......... 6 
Zine Oxide. .4...%.>.4.a4 ee ee 1260 


The compound shall be cured in mold for sixty min- 
utes at 40 pounds steam. 

The standard sample shall be compounded according 
to the above formula and cured under the same con- 
ditions. 

To be on-grade, the color of a freshly cut surface of 
the cured rubber compound containing the sample, 
shall be as white as a freshly cut surface of the com- 
pound containing the standard. 


TESTING THE PHYSICAL QUALITIES OF ZINC OXIDE 109 


PuysicaL Testing Mreruop NUMBER TWELVE 
For THE PRopERTY OF:—TENSILE STRENGTH 
AND ELONGATION. 


Description: 


The sample shall be incorporated in a rubber com- 
pound in the proportion of at least 10 volumes of pig- 
ment to 100 volumes of rubber. 

Portions of the stock shall be mold-cured for varying 
times at a constant steam pressure and tested for ten- 
sile strength and elongation in the usual way. 

The standard sample shall be compounded, cured 
and tested under identical conditions. 

To be on-grade the tensile strength and elongation of 
the cured rubber compound containing the sample, in 
the region of the optimum cure, shall not deviate from 
that of the compound containing the standard, by an 
amount greater than 10 per cent plus or minus. 

On account of the limitations in the methods, of 
testing compounded rubber, no sample shall be declared 
off grade without the confirmatory evidence of two out 
of three successive tests, starting in each case with a 
fresh portion of the pigment. 


110 ZINC OXIDE 


PuysiIcaAL TESTING MretHop NUMBER THIRTEEN 
For THE PROPERTY OF:—ABRASION RESISTANCE. 


Description: 


Cured rubber stock containing the sample at the 
approximate optimum cure shall be selected in accord- 
ance with the method outlined in Testing Method 
No. 12. 

Cured rubber stock containing the standard in a 
similar compound shall be selected in the same way. 

The two stocks shall be tested against each other on a 
standard type of abrasion machine. 

To be on-grade the abrasion resistance of the rubber 
compound containing the sample shall not deviate from 
that of the compound containing the standard by an 
amount greater than 10 per cent plus or minus. 


TESTING THE PHYSICAL QUALITIES OF ZINC OXIDE I1I11 


PuysicAL Testing Metruop NuMBER FOURTEEN 
For THE PROPERTY OF:—RATE OF CURE. 


Description: 

The criterion of the optimum cure shall be the 
maximum tensile product. 

To be on-grade the time required to reach the opti- 
mum cure by the rubber compound containing the 
sample, shall not vary in minutes from that of the 
compound containing the standard, by more than 20 
per cent plus or minus. 


PuysicaL Trestinc Mrtuop NUMBER FIFTEEN 
For THE PROPERTY OF:—PARTICLE SIZE. 


Description: 

A standard method of photomicrographic measure- 
ments of the individual particles shall be determined 
and the sample subjected to comparative measure- 
ments with the standard. 


CHAPTER 10 


STANDARD ANALYTICAL METHODS FOR TESTING THE 
CHEMICAL PROPERTIES OF ZINC OXIDE 


ANALYTICAL TESTING MretTHOoD NUMBER ONE 
For THE CONSTITUENT:—CHLORINE. 


Description: 


Ten grams of the sample are covered with water and 
10 cc. of N/10 AgNOs solution, which has been 
standardized against pure NaCl, added. Forty c.e. 
of concentrated HNOs are added and the solution 
boiled until nitrous fumes are removed. It is then 


cooled, 5 c.c. of ferric nitrate solution (1:6) added © 


and the solution titrated to a faint pink with N/10 
ammonium sulfocyanide (NH4sCNS). A blank shall 


% 


be run with the same reagents, to determine the relative _ 


strengths of the solutions. 


ANALYTICAL TESTING MrtHop NuMBER Two 
For THE CoNnsTITUENT:—H20 SoLuBLE SALTS. 


Description: 

Five grams of the sample are shaken in a 500 c.c. 
graduated flask for ten minutes with 250 c.c. of water 
at room temperature. ‘The solution is made up to 
exactly 500 c.c. and filtered through dry paper. One 
hundred c.c. of the clear filtrate are measured out, 
poured into a weighed platinum dish, and evaporated 
to dryness on a sand-bath, the contents being pro- 
tected from dust. ‘The residue is dried for one or two 
hours at 110° C., cooled and weighed rapidly. ‘The 
increase in weight represents the water soluble salts. 

112 


TESTING CHEMICAL PROPERTIES OF ZINC OXIDE 113 


ANALYTICAL TESTING MrtHop NuMBER THREE 
For THE CONSTITUENT:—Ho20 at 110° C. 


Description: 

From 2 to 5 grams of the sample, which have been 
weighed in a glass-stoppered weighing bottle, are dried 
in an oven kept at practically constant temperature of 
105° to 110° C. After cooling, the bottle is stoppered 
and weighed with its contents. The sample is returned 
to the oven for another hour and again cooled, stoppered 
and weighed as before. If there has been further loss 
of weight, this procedure is repeated until a constant 
weight is reached. ‘The loss of weight in drying is the 
H20 content at 110° C. 


ANALYTICAL TESTING MrtHop NuMBER Four 
For THE CONSTITUENT:—INSOLUBLE IN HCl. 


Description: 

A sample of 10 grams is treated with 25 c.c. of water 
and 25 c.c. of hydrochloric acid and evaporated to dry- 
ness. The residue is taken up with 50 cc. of 1:4 
hydrochloric acid and the insoluble filtered off and thor- 
oughly washed with 1:4 hydrochloric and then with 
boiling water. It is further washed with hot ammo- 
nium acetate solution and again with boiling water. 
The insoluble is then burned off and weighed. 


114 ZINC OXIDE 


ANALYTICAL TESTING MEtHopD NuMBER FIVE 
For THE CONSTITUENT:—TOTAL SULPHUR AS SOsz. 


Description: 

A sample of 13.75 grams is treated with 5-10 c.c. of 
bromine water and then dissolved in 40 c.c. of con- 
centrated HCl. The solution is boiled until the bro- 
mine has been expelled and then cooled. A small strip 
of aluminum is added and the solution heated gently 
to throw out the lead. ‘The lead and insoluble matter 
are filtered off, the filtrate neutralized with ammonia, 
then made slightly acid with hydrochloric. The solu- 
tion is heated to boiling and a slight excess of hot 10— 
per cent BaCle solution added drop by drop with con- 
stant stirring. After standing in a warm place for 
two hours or longer, it is filtered through a previously 
ignited Gooch crucible. The BaSOx. on the crucible 
is washed well with hot water, ignited in a muffle for 
thirty minutes, cooled and weighed, and the weight 
calculated to SOs. | 


TESTING CHEMICAL PROPERTIES OF ZINC OXIDE EES 


ANALYTICAL. TgestTING Metrnop NumBer SIx 
For THE CONSTITUENTS :—PbSO, (Total PbO as). 


Description: 


A sample of 2 grams for 5 per cent leaded zinc oxide 
and 4 gram for 35 per cent leaded zinc oxide shall be 
placed in 50 c.c. of water, 45 c.c. of concentrated HNO3 
added and the solution boiled. 50 c.c. more water 
and a few drops of dilute AgNOsz shall be added. The 
solution shall be placed in a Frary rapid electrolytic 
stand, using a perforated platinum cylinder anode, and 
electrolyzed for forty-five minutes at 34 amperes. At 
the end of this time the anode shall be removed quickly, 
washed with water, dried at 180° C. for twenty minutes, 
cooled and desiccated. ‘The deposit shall be weighed 
as PbO2 and calculated to PbSO.. In the case of 
35 per cent leaded zinc oxide a factor of 1.24 instead of 
1.27 shall be used in the calculation. 


ANALYTICAL TESTING MrerHop NuMBER SEVEN 
For THE CoNnsTITUENT:—PbSOsz (Total PbO as). 


Description: 

A sample of 2 grams is treated (for 35 per cent leaded 
zine oxide the sample is 1 gram) with 100 c.c. of water 
and 25 e.c. of concentrated HCl, and the insoluble 
matter filtered off. After the addition of 25 c.c. of 
1 : 1 H2SOu, the filtrate is evaporated until dense fumes 
come off, when 200 c.c. of water are added. ‘The solu- 
tion is heated until all soluble salts are dissolved, cooled, 
and 30 ¢.c. of 95 per cent alcohol added. It is allowed 
to stand overnight. The precipitate PbSOs is filtered 
off, washed first with 3 per cent H2SO. and then with 
alcohol, dried and weighed. 


116 ZINC OXIDE 


ANALYTICAL TESTING MrEtHop NuMBER EIGHT 
For THE CoNSTITUENT:—PbSOxz (Total PbO as). 


Description: 

A sample of 9.83 grams shall be placed in 50 e.c. of 
water, 45 c.c. of concentrated HNO: added and the 
solution boiled. 50 c.c. more water and a few drops 
of dilute AgNOs3 shall be added. ‘The solution is placed 
on an electrolytic stand, using a solid sheet platinum | 
anode, and electrolyzed for two hours at 1 ampere. 
At the end of this time the anode shall be removed: 
quickly, washed with water, dried at 180° C. for twenty 
minutes, cooled and desiccated. ‘The deposit shall be 
weighed as PbO: and calculated to PbSO.. 


ANALYTICAL TESTING METHOD NuMBER NINE 
For THE CONSTITUENT:—LEAD. 


Description: 

Thirty grams of the sample shall be weighed into a 
low 400 c.c. beaker, and 100 c.c. of water, and 80 c.c. of 
concentrated nitric added. After boiling for fifteen 
minutes the solution shall be diluted to about 350 c.e. 
Add a few drops of silver nitrate solution and elec- 
trolyze for at least five hours (overnight is preferable.) 

Use a solid sheet cylindrical anode with a current 
density of 1 ampere when the deposit is desired in 
five hours. Use only $ ampere if deposition is to con- 
tinue overnight. 


TESTING CHEMICAL PROPERTIES OF ZINC OXIDE LG 


ANALYTICAL TESTING METHOD NuMBER TEN 
For THE CONSTITUENT:—ZINC OXIDE. 


Description: 

Digest 1.5 grams of freshly ignited zinc wide accu- 
rately weighed, with 50 c.c. of normal sulphuric acid 
until solution is complete. Then titrate the excess 
sulphuric acid with normal potassium hydroxide, using 
methyl orange as an indicator. 

Each cubic centimeter of the above normal sulphuric 
acid used corresponds to 0.0407. gram of zine: oxide. 
Each gram of freshly ignited zinc oxide must corre- 
spond to not less than 24.3 ¢.c. of normal sulphuric acid. 


ANALYTICAL TESTING MrtHop NuMBER ELEVEN. 
For THE CONSTITUENT:—H20 SoLuBLE: ALKALI. 


Description: 

Digest 1 gram of zinc oxide in a small flask with 
10 c.c. of boiling distilled water. Add two. drops of 
phenolphthalein indicator. Not more than 1 c.c. of 
tenth normal hydrochloric acid shall be required to. dis- 
charge any red color that may be produced. 


118 ZINC OXIDE 


ANALYTICAL TESTING METHOD NUMBER TWELVE 
For THE CONSTITUENT:—ToTaL HeAvy METALS. 


Description: 

Weigh 1 gram of zinc oxide into a test-tube of about 
40 ¢.c. capacity and about 2.5 cms. in diameter, add 
about 10 c.c. of distilled water and dissolve with a very 
slight excess of hydrochloric acid. Heat the solution 
to about 50° C., add an equal volume of freshly pre- 
pared saturated solution of hydrogen sulphide in water. 
Stopper the test-tube, thoroughly mix the contents and 
allow to stand for half an hour in a moderately warm 
place (about 35° C.). At the end of this time the mix- 
ture should still possess the odor of hydrogen sulphide; 
if not, it shall be thoroughly saturated with the gas and 
again set aside for half an hour. The color produced 
~ shall not be greater than that observed by a blank test 
made in the same manner and with the same quantities 
of the reagents (omitting the zinc oxide). The solu- 
tion shall be viewed crosswise by reflected light while 
held against white surfaces. A slight turbidity due to 
separation of sulphur from the hydrogen may occur. 


TESTING CHEMICAL PROPERTIES OF ZINC OXIDE 119 


ANALYTICAL TESTING MeEetTHopD NuMBER THIRTEEN 
For THE CONSTITUENT:—SOz2 (Red. Power Equiv. to). 


— Description: 

A sample of 3.2 grams is treated with 100 c.c. of 
cold water and 100 c.c. of boiling water and some starch 
solution added as an indicator. Iodine solution (N/100) 
is run in until the end point is near, when 25 c.c. of 
concentrated hydrochloric acid are added and the titra- 
tion with the iodine solution finished. 


ANALYTICAL TESTING METHOD NUMBER’ FOURTEEN 
For THE CONSTITUENT :—INSOLUBLE IN ACETIC ACID. 


Description: 


Ten grams of zinc oxide shall be weighed into a 250 
c.c. beaker; 100 c.c. of distilled water shall be added 
and the oxide stirred. 100 c.c. of 50 per cent acetic. 
acid shall then be added, followed by 10 c:c. of strong 
ammonia water. The whole shall be stirred until all of 
the zinc oxide has dissolved, when it is allowed to stand 
for two or more hours. The insoluble residue is filtered 
on a weighed and dried Gooch crucible, and washed 
first with hot 10 per cent acetic acid, then with hot 
distilled water. The crucible is dried at 110° C. and 
reweighed; the gain in weight being the amount of 
insoluble matter in the 10 grams. 


120 ZINC OXIDE 


ANALYTICAL TESTING METHOD NUMBER FIFTEEN . 
For THE CONSTITUENT:—TOTAL SULPHUR AS SQO3. 


Description: 


A sample of 6.86 grams is mixed with 17 grams of 
sodium bicarbonate, 200 ¢c.c. of water and 5 to 10 @.@ 
of bromine water added. The solution is boiled gently 
for fifteen minutes and set in a warm place until the 
precipitated carbonates settle. The latter are filtered. 
off and washed thoroughly with hot water. ‘The filtrate 
is boiled until the bromine is expelled and made slightly 
acid with hydrochloric. The solution is heated to boiling 
and a slight excess of hot 10 per cent BaClz solution 
added drop by drop with constant stirring. After 
standing in a warm place for two hours or longer, it is 
filtered through a previously ignited Gooch crucible. 
The BaSO. on the crucible is washed well ‘with hot 
water ignited in a muffle for thirty minutes, cooled 
and weighed, and the weight calculated to SOs. 


ANALYTICAL TESTING MrtrHop NuMBER SIXTEEN 
For THE CONSTITUENT:—INSOLUBLE IN AcETIC ACID, _ 


Description 


Weigh 10 grams of the sample into a 250 c.c. beaker. 
Intimately mix with 50 c.c. of water, then add 50 e.c. 
of 50 per cent acetic acid. Allow to stand at room 
temperature for one-half hour, agitating frequently, then 
filter through a weighed Gooch crucible. Wash with 
luke-warm 10 per cent acetic acid, then with hot water. 
Dry at 110° C. and weigh. 7 


TESTING CHEMICAL PROPERTIES OF ZINC OXIDE = 121 


ANALYTICAL TESTING METHOD NUMBER SEVENTEEN 
For THE CONSTITUENT:—ARSENIC. 


Description 


Arsenic, reported as As2Qz, shall be determined by 
the Gutzeit method, using apparatus as shown in 
Scott’s “Standard Method of Chemical Analysis,” 
Second Edition, Revised, page 46. 

Two grams of the sample shall be weighed into a 

150-¢.c. beaker and 50 c.c. of dilute sulphuric acid 
(1 volume arsenic free concentrated sulphuric acid, 
to 10 volumes of water) added and after complete 
solution has been effected, boiled for five minutes. 
Then 1 c.c. of ferrous sulphate solution (17.5 grams 
FeSO4. 7H20O in 100 c.c. water) and 1 ¢.c. of stannous 
chloride solution (40 per cent SnCle in hydrochloric 
acid) shall be.added. 
_ The solution shall then be cooled, poured into the 
60 ¢.c. bottle and the beaker washed with a minimum 
amount of water. The test strip of mercuric chloride 
paper shall then be placed in the upper tube, 2 grams of 
20-mesh arsenic free zinc added to the solution in the 
bottle and the upper part of the apparatus immediately 
attached. After thirty minutes the depth of coloration 
of the test-paper shall be compared with standard test- 
papers from tests made using the same amounts of 
solutions and zinc but with known amounts of arsenic 
added. The mercuric chloride test-paper is made 
by moistening filter paper with 5 per cent solution of 
mercuric chloride, sightly pressing out the excess, dry- 
ing, cutting accurately to size and keeping it tightly 
stoppered in dark glass bottles. 


CHAPTER 11 


UNITED STATES GOVERNMENT SPECIFICATIONS AND TEST- 
ING METHODS 


UNITED STATES GOVERNMENT SPECIFICATION 
For Zinc OxipE, DRY AND IN Paste. 


General: 


Zinc oxide may be ordered in the form of dry pig- 
ment or paste ground in linseed oil. Purchases shall 
be made on the basis of net weight. 

The pigment may be American Process zine oxide, 
made direct from the ore, or French Process zine oxide, 
made from spelter. The contract shall state which 
kind is desired. 

The color and color strength when specified shall be 
equal to samples mutually agreed upon by buyer and 
seller. 

The pigment shall meet the following specifications. 

Coarse particles retained on Standard 325 screen. 
Max. 1 per cent. 


American Process French Process 


Maximum! Minimum Maximum] Minimum 
Per cent | Per cent | Per cent ; Per cent 








Zine Oxide ic1 ge ies Ce ee 985 (ae 99 
Total sulphur. - 5.9 ee O21 gu ee 0.10 
Total impurities, moisture. 2.00 joe 1.00 





UNITED STATES GOVERNMENT SPECIFICATIONS 123 


The paste shall be made by thoroughly grinding the 
above pigment with pure raw or refined linseed oil. 
The paste shall not cake in the container.and shall break 
readily in oil to form a smooth paint of brushing con- 
sistency. 

The paste shall consist of: 





Maximum, | Minimum, 
Per Cent Per Cent 


ee ee ne acs kd win pe wae 86 82 


FRE Cee a ae ee 18 14 
Coarse particles and skins.............. 125 

Moisture and other volatile matter...... 0.5 
Sampling: | 


It is mutually agreed by the buyer and seller that a 
single package out of each lot of not more than 1000 
packages shall be taken as representative of the whole. 

With the dry pigment, this package is to be opened 
by the inspector and a sample of not less than 5 pounds 
taken at random from the contents and sent to the 
laboratory for test. When requested, a duplicate 
sample may be taken from the same package and 
delivered to the seller, and the inspector may take a 
third sample to hold for test in case of dispute. 

With the paste, whenever possible, an original 
unopened container shall be sent to the laboratory; 
and when this is for any reason not done, the inspector 
shall determine by thoroughly testing with a paddle 
or spatula whether the material meets the require- 
ment regarding not caking in the container. After 
assuring himself that the paste is not caked in the can, 
the inspector shall draw a sample of not less than 


124 33 | ZINC OXIDE 


pounds of the thoroughly mixed paste, place it in a 
clean, dry metal or glass container which must be filled 
with the sample, closed with a tight cover, sealed, © 
marked and sent to the laboratory for test with the 
inspector’s report on caking in the container. 


LABORATORY EXAMINATION OF Dry PIGMENT. 


(1) Color.—Take 5 grams of the sample, add 1.5 c.c- 
of linseed oil, rub up on a stone slab or glass plate with a 
flat-bottomed glass or stone pestle or muller to a uni- 
form smooth paste. ‘Treat in a similar manner 5 grams 
of the standard sample of zinc oxide. Spread the two 
pastes side by side on a clear colorless glass plate and 
compare the colors. If the sample is as white as or 
whiter than the “ standard,” it passes this test. If the 
“standard ”’ is whiter than the sample the material 
does not meet the specification. — 

(2) Color Strength.—Weigh accurately 0.01 gram of 
lampblack, place on a large glass plate or stone slab, 
add 0.2 c.c. of linseed: oil, and rub with a flat-bottomed 
glass pestle or muller, then add exactly 10 grams of the 
sample and 2.5 c.c. of linseed oil, and grind with a 
circular motion of the muller 50 times; gather up with a 
sharp-edged spatula and grind twice more in a like 
manner, giving the pestle a uniform pressure. ‘Treat 
another 0.01 gram of the same lampblack in the same 
manner except that’ 10 grams of the standard sample 
zinc oxide shall be used instead of the 10 grams of the 
sample. Spread the two pastes side by side on a glass 
microscope slide and compare the colors. If the sample 
is as light as or lighter in color than the “ standard,” 
it passes:this test. If the “‘ standard” is lighter in 


UNITED STATES GOVERNMENT SPECIFICATIONS 125 


color than the sample, the material does not meet the 
specification. 

(3) Coarse Particles.—Dry in an oven at 105 to 110° 
C. a 325 mesh screen, cool and weigh accurately. 
Weigh 10 grams of the sample; dry at 100° C., trans- 
fer to a mortar, add 100 c.c. kerosene, thoroughly 
mix by gentle pressure with a pestle to break up the 
lumps, wash with kerosene through the screen, break- 
ing up all of the lumps but not grinding. After washing 
with kerosene until all but the particles which are too 
coarse to pass through the screen have been washed 
through, wash all kerosene from the screen with either 
or petroleum ether, heat the screen for one hour at 105 
to 110° C., cool and weigh. 
~ (4) Qualitative Analysis.—Test for matter insoluble 
in hydrochloric acid, for lead, calcium, etc., by regular 
methods of qualitative analysis. 

(5) Zine Oxide.—With samples free from impurities 
ignite a weighed sample and calculate the residue as 
zinc oxide. With samples containing impurities, pro- 
ceed as follows: Weigh accurately about 0.25 gram, 
transfer to a 400 c¢.c. beaker, moisten with alcohol, 
dissolve in 10 c¢.c. of hydrochloric acid and 20 c.c. of 
water and titrate with standard potassium ferrocyanide 
following the procedure used in standardizing this 
reagent. 

(6) Total Sulphur—Weigh accurately about 10 
grams of the sample. Moisten with a few drops of 
aleohol, add 5 c.c. of bromine water (saturated solution 
of bromine), then concentrated hydrochloric acid in 
excess, boil to expel the bromine, and dilute to about 
100 c.c. (Material complying with the specifications 
should all go into solution; if insoluble matter remains, 


126 ZINC OXIDE 


filter and examine by appropriate methods.) Make 
alkaline with ammonia, then just acid with hydrochloric 
acid, heat to boiling-point and add about 10 c.c. of 
hot barium chloride solution. Let stand several 
hours (overnight), filter on a weighed Gooch crucible, 
wash thoroughly with hot water dry, ignite, and weigh 
with BaSO.. Calculate 8 (BaSXO,0.1373=8). 


LABORATORY EXAMINATION OF PASTE. 


(1) Caking in Container.—When an original package 
is received in the laboratory, it shall be weighed, opened 
and stirred with a stiff spatula or paddle. The paste 
shall be no more difficult to break up and show no more 
caking than a normal good grade of zinc oxide paste. 
The paste shall be finally thoroughly mixed, removed 
from the container, the container wiped clean, and 
weighed. This weight subtracted from the weight of 
the original package gives the net weight of the con- 
tents. A portion of the thoroughly mixed paste shall 
be placed in a clean container and the portions for the 
remaining tests promptly weighed out. 

(2) Mixing with Linseed Orl—One hundred grams 
of the paste shall be placed in a cup, 35 c.c. of linseed 
oil added slowly with a careful stirring and mixing with 
a spatula or paddle. The resulting mixture must be 
smooth and of good brushing consistency. 

(3) Movrsture and Other Volatile Matier—Weigh 
accurately from 3 to 5 grams of the paste into a tared 
flat-bottomed dish, about 5 cm. in diameter, spreading 
the paste over the bottom. Heat at 110° C. for one 
hour, cool and weigh. Calculate loss in weight as per- 
centage of moisture and other volatile matter. 


UNITED STATES GOVERNMENT SPECIFICATIONS 127 


(4) Per Cent Pigment—Weigh accurately about 
15 grams of the paste into a weighed centrifuge tube. 
Add 20 to 30 c.c. of ‘ extraction mixture ”’ (see Rea- 
gents), mix thoroughly with a glass rod, wash the rod 
with more of the extraction mixture, and add sufficient 
of the reagent to make a total of 60 c.c. in the tube. 
Place the tube in the container of the centrifuge, sur- 
rounded with water, and counterbalance the container 
of the opposite arm. with a similar tube or a tube of 
water. Whirl at a moderate speed until clear. Decant 
the supernatant liquid. Repeat the extraction twice 
with 40 c.c. portions of extraction mixture, and once 
with 40 c.c. of ether. After drawing off the ether, set 
the tube in a beaker of water at 80° C. or on top of a 
warm oven for ten minutes, then in an oven at 110° C. 
to 115° C. for two hours. Cool, weigh, and calculate 
percentage of pigment. 

(5) Examination of Pigment.—Grind the pigment 
from (4) to a fine powder, pass through a No. 80 mesh 
screen to remove any “ skins,” preserve in a stoppered 
tube and apply tests Nos. 4, 5, and 6, of Laboratory 
Examination of Dry Pigment. If required, apply tests 
Nos. 1 and 2 also, with a portion of pigment extracted 
from the standard paste in exactly the same manner as 
in extracting the sample. 

(6) Preparation of Fatty Acids —To about 25 grams 
of the paste in a porcelain casserole add 15 c.c. aqueous 
sodium hydroxide (see Reagents), add 75 c.c. of ethyl 
alcohol, mix and heat uncovered on a steam bath until 
saponification is complete (about one hour). Add 
100 ¢c.c. of water, boil; add an excess of sulphuric acid 
of specific gravity 1.2 (8 to 10 c.c. will usually suffice), 
boil, stir, and transfer to a separatory funnel to which 


128 ZINC OXIDE | 


some water has been previously added. Draw off as 
much as possible of the acid aqueous layer, wash 
once with water; then add 50 c.c. of water and 50 c.c. 
of ether. Shake very gently with a whirling motion to 
dissolve the fatty acids in the ether, but not violently, 
so as to avoid forming an emulsion. Draw off the 
aqueous layer and wash the ether layer with one 15 c.c. 
portion of water and then with 5 c.c. portions of water 
until free from sulphuric acid. Then draw off com- 
pletely the water layer. ‘Transfer the ether solution 
to a dry flask, and add 25 to 50 grams of anhydrous 
sodium sulphate. Stopper the flask and'let stand with 
occasional shaking at a temperature below 25° C. until 
the water is completely removed from the ether solu- 
tion, which will be shown by the solution becoming 
perfectly clear above the solid sodium sulphate. Decant 
this clear solution (if necessary through a dry filter 
paper) into a dry 100 c.c. Erlenmeyer flask. Pass a 
rapid current of dry air (pass through CaCls tower) 
into the mouth of the Erlenmeyer flask and heat to 
a temperature below 75° C. on a dry hot plate until the 
ether is entirely driven off. The fatty acids prepared 
as above should be kept in a stoppered flask and exam- 
ined at once. Note.—It is important to follow all of 
the details, since ether generally contains alcohol and 
after washing with water always contains water. It is 
very difficult to remove water and alcohol by evapora- 
tion from fatty acids, but the washing of the ether solu- 
tion and subsequent drying with anhydrous sodium 
sulphate removed both water and alcohol. Ether, in 
the absence of water and alcohol, is easily ree 
from the fatty acids by gentle heat. 

(7) Tests for Mineral Oil and Other Unsaponifiable 


UNITED STATES GOVERNMENT SPECIFICATIONS 129 


Matter.—Place 10 drops of the fatty acid (6) in a 50 c.e. 
test-tube, add 5 c¢.c. of alcoholic soda (see Reagents), 
boil vigorously for five minutes, add 40 c.c. of water, 
and mix; a clear solution indicates that not more 
than traces of unsaponifiable matter are present. If 
the solution is not clear, the oil is not pure linseed oil. 

(8) Iodine Number of Fatty Acids——Place a small 
quantity of the fatty acids (6) in a small weighing 
burette or beaker. Weigh accurately. Transfer by 
dropping about 0.15 gram (0.10 to 0.20 gram) to a 
500 c.c. bottle having well-ground glass stopper, or an 
Erlenmeyer flask having a specially flanged neck for the 
iodine test. Reweigh the burette or beaker and 
determine the amount of the sample used. Add 10 
c.c. of chloroform. Whirl the bottle to dissolve the 
sample. Add 10 c.c. of chloroform to two empty 
bottles like that used for the sample. Add to each 
bottle 25 c.c. of the Hanus solution (see Reagents) 
and let stand, with occasional shaking, for one-half 
hour. Add 10 c.c. of the 15 per cent potassium- 
iodide solution and 100 c.c. water, and titrate with 
standard sodium thiosulphate, using starch as an indi- 
eator. The titrations on the two blank tests should 
agree within 0.1 c.c. From the difference between the 
average of the blank titrations and the titration on the 
sample and the iodine value of the thiosulphate solu- 
tion, calculate the iodine number of the sample tested. 
(Iodine number in centigrams of iodine to.1 gram of 
sample.) If the iodine number is less than 170, the 
oil does not meet the specification. 

(9) Coarse Particles and “ Skins.’’—Weigh an amount 
of the paste containing 10 grams of pigment (see above), _ 
add kerosene, and wash through a No. 325 screen as in 


130 ZINC OXIDE 


Dry Pigment Examination No. 3. The residue is 
reported as ‘‘ coarse particles and skins.”’ 


REAGENTS. 


(1) Extraction Mixture.— 


10 volumes of ether (ethyl ether) 
6 volumes of benzol 
4 volumes methyl alcohol 
1 volume of acetone. 


(2) Aqueous Sodium Hydroxide——Dissolve 100 grams 
sodium hydroxide in distilled water and dilute to 300 c.c. 

(3) Standard Sodium Thiosulphate Solution.—Dis- 
solve pure sodium thiosulphate in distilled water that 
has been well boiled to free it from carbon dioxide, in 
the proportion of 24.83 grams crystallized sodium thio- 
sulphate to 1000 c.c. of the solution. It is best to let 
this solution stand for about two weeks before stand- 
ardizing. Standardize with pure resublimed iodine. 
(See Analytical Chemistry, Treadwell-Hall, Vol. 2, 
3d edition, page 646.) This solution will be approx- 
imately decinormal, and it is best to leave it as it is 
after determining the exact iodine value rather than to 
attempt to adjust it to exactly decinormal. Preserve 
in a stock bottle provided with a guard tube filled with 
soda lime. 

(4) Starch Solution.—Stir up 2 or 3 grams of potato 
starch or 5 grams soluble starch with 100 c.c. of 1 per 
cent salicylic acid solution, add 300 c.c. to 400 c.c. 
boiling water, and boil the mixture until the starch 
is practically dissolved, then dilute to 1 liter. 


UNITED STATES GOVERNMENT SPECIFICATIONS 131 


(5) Potassium Iodide Solution.—Dissolve 150 grams 
of potassium iodide free from iodate in distilled water 
and dilute to 1000 c.c. 

(6) Hanus Solution.—Dissolve 13.2 grams of iodine 
in 1000 c.c. of 99.5 per cent glacial acetic acid which 
will not reduce chromic acid. Add enough bromine 
to double the halogen content, determine by titration 
(3 ¢.c. bromine is about the proper amount). The 
iodine may be dissolved by the aid of heat, but the 
solution should be cold when the bromine is added. 

(7) Alcoholic Sodium Hydroxide Solution.—Dissolve 
pure sodium hydroxide in 95 per cent ethyl alcohol in 
the proportion of about 22 grams per 1000 c.c. Let 
stand in a stoppered bottle. Decant the clear liquid 
into another bottle and keep well stoppered. ‘This 
solution should be colorless or only slightly yellow when. 
used, and it will keep colorless longer if the alcohol is 
previously treated with sodium hydroxide (about 80 
grams to 1000 c.c.) kept at about 50° C. for fifteen days 
and then distilled. 

(8) Uranyl Indicator for Zinc Titration.—A 5 per 
cent solution of uranyl nitrate in water or a 5 per cent 
solution of uranyl acetate in water made slightly acid 
with acetic acid. 

(9) Standard Potassium Ferrocyanide.-—Dissolve 22 
grams of the pure salt in water and dilute to 1000 c.c. 
To standardize transfer about 0.2 gram (accurately 
weighed) of pure metallic zinc or freshly ignited pure 
zine oxide to a 400 c.c. beaker. Dissolve in 10 c.c. 
hydrochloric acid and 20 ¢.c. water. Drop in a small 
piece of litmus paper, add ammonium hydroxide until 
slightly alkaline, then add hydrochloric acid until just 
acid, and then add 8 c.c. strong hydrochloric acid. 


1382 ZINC OXIDE 


Dilute to about 250 c.c. with hot water and heat nearly 
to boiling. Run in the ferrocyanide solution slowly 
from a burette with constant stirring until a drop: 
tested on a white porcelain plate with a drop of uranyl 
indicator shows a brown tinge after standing a minute. 
A blank should be run with the same amounts of 
reagents and water as in the standardization. The 
amount of ferrocyanide solution required for the blank 
should be subtracted from the amounts used in the 
standardization and in titration of the sample. The 
standardization must be made under the same condi- 
tions of temperature, volume, and acidity as obtained 
when the sample is titrated. , 

(10) Barium Chloride Solution.—Dissolve 100 grams 
of pure crystallized barium chloride in water and dilute 
to 1000 c.c. 


UNITED STATES GOVERNMENT SPECIFICATION 
For Zinc Oxipe (LEADED Zinc OxIDE) 
Dry OR IN PASTE. 


General. 


Leaded zinc oxide, frequently known as leaded zine, 
consists of zinc oxide and varying amounts of lead 
compounds. It may be ordered in the form of dry 
pigment or paste ground in linseed oil. Purchases shall 
be made on the basis of net weight. 

The pigment may be high-leaded zine oxide or low- 
leaded zinc oxide. The contract shall state what kind 
is desired. The color and color strength when specified | 
shall be equal to samples mutually agreed upon by the 
buyer and the seller. 


UNITED STATES GOVERNMENT SPECIFICATIONS 133 


The pigment shall meet the following requirements: 


High Leaded Low Leaded 


Max. | Min. Max. Min. 








Per Cent |Per Cent |Per Cent | Per Cent 
Uf CAE a! Sea) 6 rr rr SUD ty igihat, 93 
Water soluble salts........... PI RAPE ae yd 1.0 
Total impurities, inc. moisture.| 1.5 | ...... 1.5 


The balance to be normal or 
basic lead sulphate......... 





Coarse particles retained on No. 325 mesh screen. 
Max. 1.0 per cent min. | 

The paste shall be made by thoroughly grinding the 
pigment with pure raw or refined linseed oil. The 
paste shall not cake in the container and shall break 
up readily in oil to form a smooth paint of brushing 
consistency. ‘The paste shall consist of: 


Maximum, | Minimum, 
Per Cent Per Cent 


MRSMMIREIRR es oe wd ns wk ees ec ee 88.0 
PS SES GO A es 2 Oe es ae a ee 12.0 
Moisture and other volatile matter...... 5 


134 ZINC OXIDE 


SAMPLING. 


The sampling method and procedure for leaded zine 
oxide is the same as given for lead free zinc oxide. 


LABORATORY EXAMINATION OF Dry PIGMENT 


(1) Color—wUse the same test as outlined in labora- 
tory procedure for lead free zine oxide. 

(2) Color Strength.—Use the same test as outlined in 
laboratory procedure for lead free zinc oxide. 

(3) Qualitative Analysis—Test for matter insoluble 
in hydrochloric acid, lead, calcium, carbon dioxide, etc., 
by regular methods of qualitative analysis. 

(4) Moisture.—Place 1 gram of the sample in a wide- 
mouthed short weighing tube provided with a glass 
stopper. Heat with stopper removed for two hours at a 
temperature between 100 to 105° C. Insert stopper, 
cool and weigh. Calculate loss in weight as moisture. 

(5) Water Soluble Salts—To 10 grams of the pig- 
ment in a 500 c.c. volumetric flask add 200 c.c. of water, 
boil for five minutes, nearly fill the flask with hot water, 
allow to cool, fill to mark, mix, filter through a dry 
paper, discard the first 50 c.c. of filtrate, transfer 100 c.c. 
of the filtrate (corresponding to 2 grams of the sample) 
to a weighing dish, evaporate to dryness, heat for one 
hour in an oven at 105 to 110° C., cool, and weigh, cal- 
culate the percentage of water soluble salts. | 

(6) Zinc Oxide.—Weigh accurately about 0.3 gram of 
the pigment, transfer to a 400 c.c. beaker, add 30 c.c: of 
hydrochloric acid (1 : 2), boil for two or three minutes, 
add 200 ¢c.c. of water and a small piece of litmus paper; 
add ammonium hydroxide until slightly alkaline, 


UNITED STATES GOVERNMENT SPECIFICATIONS 135 


render just acid with hydrochloric acid, then add 8 c.c. 
of strong hydrochloric acid, heat nearly to boiling, and 
titrate with standard potassium ferrocyanide as in the 
standardizing solution. (See Reagent No. 4.) Cal- 
culate total zinc as ZnO. 

® (7) Calculations —If, as will be the case with mate- 
rial complying with the specification, no metal but zinc 
and lead are found by qualitative analysis tests, add 
the percentage of ZnO, moisture, and water soluble 
salts and subtract the sum from 100. Call the remainder 
“normal and basic lead sulphate.”’ 


LABORATORY EXAMINATION OF PASTE 


(1) Caking in the Container.—Use the same test as 
outlined in laboratory procedure for lead-free zinc oxide 
in paste. 

(2) Mixing with Innseed Oil.—Use the same test as 
outlined in laboratory procedure for lead-free zinc oxide 
in paste. 

(3) Movrsture and Other Volatile Matter.—Use the 
same test as outlined in laboratory procedure for lead- 
free zinc oxide in paste. 

(4) Percentage of Pigment.—Use the same test as 
outlined in laboratory procedure for lead-free zinc oxide 
in paste. 

(5) Examination of Pigment.—Grind the pigment 
from (4) to a fine powder, pass through a No. 80 mesh 
screen to remove any ‘‘ skins,’”’ preserve in a stoppered 
tube, and apply tests Nos. 4, 6, 7 and 8 of the procedure 
outlined in Laboratory Examination of Dry Pigment. 
If required, apply tests 1 and 2 of that procedure in 
comparison with a portion of pigment extracted from 


136 ZINC OXIDE 


the standard paste in exactly the same manner as in 
extracting the sample. 

(6) Preparation of Fatty Acids.—Use the same test 
as outlined in laboratory procedure for lead-free zinc 
oxide in paste. 

(7) Test for Mineral Oil and other Unsaponifiable 
Matter —Use the same test as outlined in ee 
procedure for lead-free zine oxide in paste. 

(8) Iodine Number of Fatty Acids——Use the same 
test as outlined in laboratory procedure for sees 
zinc oxide in paste. 

(9) Coarse Particles or “ Skins.”’—Use thet same Gone 
as outlined in laboratory procedure for lead-free zinc 
oxide in paste. 


REAGENTS 


(1) Uranyl Indicator ‘for Zinc Titration —A 5 per. 
cent solution of uranyl nitrate in water or a 5 per cent 
solution of uranyl acetate in water made mee acid 
with acetic acid. 3 

(2) Standard Potassium Ferrocyamde.—Use the same 
procedure as outlined under Reagents for lead-free 
zinc oxide. 

(3) Barium Chloride Solution. ~-Disaohve 100 grams 
of pure crystallized barium chloride in water and dilute 
to 1000 c.c. 

(4) Standard Sodium Thiosulphate Solution. wate the 
same procedure as outlined under Heteenie for lead- 
free zinc oxide. : 

(5) Starch Solution.—Use the same oindeeties as out- 
lined under Reagents for lead-free zine oxide. 


UNITED STATES GOVERNMENT SPECIFICATIONS 137 


(6) Haxtraction Mixture-—Use the same procedure as 
outlined under Reagents for lead-free zinc oxide. 

(7). Aqueous Sodium Hydroxide.—Dissolve 100 grams 
of sodium hydroxide in distilled water and dilute to 
300 ¢.c. , 

(8) Potasstum Iodide Solution.—Dissolve 150 grams 
of potassium iodide free from iodate, in distilled water 
and dilute to 1000 c.c. 

(9) Hanus SolutionUse the same procedure as 
outlined under Reagents for lead-free zine oxide. 

(10) Alcoholic Sodium Hydroxide Solution.—Use the 
same procedure as outlined under Reagents for lead- 
free zinc oxide. 








A 

PAGE 
PeAAEPemiECtaNGe. t68b Ol. 6... ee tec ee ce vce eeteeeny 110 
pcewdermaa ansoupleim, test for... 006 el ke ee te ce 119, 120 
DRReMEIISEBIMOCUICHION OF ZINC, .., .. 0 knee ee eke eee tees eswens 3 
ares, LOSE LOT... ccs ww cc eect ce ae nets 117 
American process zinc oxide (see Zine oxide)............... 49, 59, 81 

Analytical testing method: 
Beret CerreNCeAOGOULIIG 10S is cc occu vice vee eoweceacn’s 119 
Neer eU OIG WALET. oe. se eres st oe eee ele bees seeecs 117 
RE one Es oe care sen oa ete ba ddaeease ee 121 
aE eRe tt od ny viele is sgh ee eeeekenes 112 
Sree rie acid, Msohible in. J... we eee ewe here 113 
RRS Re Ce ICTHCI faeces le es fee a ae nev ce ate 119, 120 
Pregiinie Wen VOrOCDIOTIC ACIG of. be ee eet eee anne 113 
Teed ae 34% NPT re REP Nl eg Stee wee ee Sah ver tos 116 
Lead sulphate (PbSo., total PbO as).....:............ 115, 116 
neue CAV VG es itv ews b sus ueeneee ss 118 
MR EME ee a ds ee vec gadec Poa heh egle Hts woe a es 113 
EE ose, cc hc octlcmus sea eee eae 112 
(Sho ECTS 0S) FS a ocean 114, 120 
MMER RR ele ee ce ei! Bie ks ES. ba eee 119 
RR ee aig se gk face ee a end pein be ate Lae. 
sR RPE LINICNS ree. hs. Be keds e ls Ga va Peed avec ne ne 2 
Reet TV OTOXING. sy os os ee cea eae ee pee vee 130, 137 
Arsenic, test for...... i cB ssw acest ON oe hoe Ee 121 

B 

Be GOB tea? «vin inghs «5 +508 soe are Toye ¢. 08, 78 
French process zin¢ oxide...) 03 320..0.6% Cr tane meee ! 
Bos ici her os ok Oh Pet Ee ODP TapeeTs 
Barium chloride solution... .. sity peas es ak tee mone he 132,)0136 
OSI] I a a en Ct a fy ap ee uaa pels Saree DN EET. 
1G ERS a: 3, 3.7 BBs 2 8A oe ctu Ar, On A RAE ae RL ae ED 
PX TTALIV BES OF © oc c5. cig esha Maun’ Wie ns bleep eee eRe oO es |e 11 


140 INDEX 


PAGE 
Blending. 0. 2.4 0002 ss eae 2 ne pen oi omen in 71 
Blow holes... 5c ccg se hese ys cae’ 1s ece ) Re 80 
Bolting machine... 3... eas oe ee ee ee 72 
Brightness, test for... 4.45 taxes © os cee oe 4c 98 
Briquetted ore... . .. 26.554 sales ap a a oy ieee ae ene 75 
Burden, furnace... 0.344404 go siae e » es ok eae 7 
C 
Cadmia, zine accretions... .. . ss «+ +d ss + «dl geeneee nae 14 
Cadimiam. .. oo cs ee cb vous elas oo ale a o> opengl nr 62 
Caking mn contaimer .... 006 52. 30 %s oo w+ cae 126 
Calamine zine ores... 0.3. sass ss seas 0 ole 13 
Candles, zine. 2.2 6h ia wv coe son 4 wee eine 60 
Carbonate ZINC OF@) oo... 6 oe vos Gis ws oe ids 
Champion, John and William... .. 0. 1.4. cunueiees tenn 14 
Charge Cars... i pee ee ee wt ce 0 on een 83 
CTANCG. os a eed eh ole wie be Ok ee ee Ne nee 56 
Chlorine, test for. . 02 5.)5.0 25 wy as» ace 0 0 overage ete 112 
Collection hopper, French process zine oxide.................-. 43 
Combustion chamber. . 0... 44. sca «+ i «0/0 eee 81 
Color, in rubber, test for... 2. ...0.:. <« Jos gee 108 
Strength, test for. : 05... . sis fee oe 124, 134 
Test: of... cose sen. s « Suspense 07, 194: 5132 
Condenser, Spelter furnace,......... <. « «<5 seen 33 
Rd. oy esie ae ald eae as ae os 0h or ae 34 
Support... .¢.i 0.0 ees ss we ate 2 2 ee 33 
Temperature of... 23... .:0 5: so 37 
Cooling pipes... 6... 0s. va aie ee ae 67, 78, 86 
Cure, rate of, test for... 2.05.0... .0 «kp ue rece eh 
Cyclone blower. 02.006 eee oes ee oe J rrr 
D 
Down legs... oie ees eo dy frst ee 5 er 61, 65 
| D)cth 1). eS SE 65, 78 
(Extraction imixturés 5 cic chss sce oa So) en ', 180) 13704 
F. 
Fans, zine exide plans... .. eur aS Ce outa ae «woke ee i, BS 


Fatty acids, iodine number of...... ... s.. + «suse a 129, 136 


INDEX 141 


PAGE 
ERCP ER TCUGTARION Oly. eevee a oie eee Geddes ee ethene 127, 136 
SSO GS 9000 a 18 
ONE SS ea ae nay 
Beeb OrGers FING OXINE Oc. ie ee ee be te ee le we 38 
(POGnuCaleOnstitnente. 64.000. es. as ce 90 
ROE Es SONY lias sacs) aiid ig ng nyeye st dio 39 
PIER ATOO 4 mie entice eke ag toe ees 40 
PAVSICAl PYOPETUICS, os ysl is ele ws 90 
VCS SP Ue ta Cee Coed ea 46 
ee a iy ede hye a Sp ok Ad pp ore ence dalees 53, 81 
Furnace, American process zine oxide: . 
SIE Se a te Acar Pet eek Seek vp beet 59 
eer ee Ree, Gi hac av ka doe es oe hae 81 
Meaitace, .merican zinc oxide block. s.4..6.0. 6.5. be oa ees 57 
ER GCOU CORIO IT Bd duci ce cae 77 
LRSVELING OTHtES 5 c44) eda 75 
Bins, American process zinc oxide plant............ 55, 77 
RMERURATMEOCK £00 ea ca vas ce a a chs GBM Saad ges 63, 77 
eM rr A. Sk we eon Ca Pla Woke ts ae Se 56 
RRM IOGE sy CNY sacs hbo Se Sueded dew oe 64 
Ree I ert ge Sy See Sed PP ge LAS os 28 
eetare RMT IOC DOCK on. so aac Ok wnt 0 pila be gees Re 63 
G 
RE Pa ivi p ieee sctccesbwewaeaes 65 
ene eR ce. a fark wie oie bd ym 4 ae Mons wel Os wwe 30, 31 
ey ey Rr 13 
Government specifications: 
DO MRTOC INC OXIUIC. 6 ins few eee tunes Bet ek. ine Bo he OR 123 
Me, OSU Seco hein aie si 5A RAS WORSE LORDS TRG 132 
I 08 ein ka ok tC Ais k oe PROD win ein toy ace OR 85 
RSME TC OKIE ge yay oss sv ss 6d thee e vad s cea tas 45 
. H 
EERIE LATRINES os gs 53s 9s 9s Mephtd Chak ga oo8 <a obea REO OS oa ey Rhee oles? 
MERRION CL ERG OL 0. Surle tina i Ss 4s tohabote OMe Renee ee yk ae betes 100, 103 
ENCE STN OLC 94 shes, ae die. oie WES Pls Woe kate ee oF 13 
I 
SOOT Ol Pitty ROME oy date oo o-4t a8 kd PUNE bo ns 4.5 ois a wes 129 
Inépiible in hydrochloric acid, test:for......... 06.0.0. e eee eee 113 


PoetiC Bed) test LOR eh Nena Fad eer s/o 119, 120 


142 INDEX 


J 
JONES oc eins dine vive e vb see bales seg 9s oie cleo enn 7 
Joplin, Missouri, zinc district... ... 22... . saree eee 21 
K 
JC A151) ts EIEN 4 
L 
Lawson, Dr. [saa ...0/¢sa-. coc as vic's ceo 0s fe ep ne 4 
Lead, test for... csc. c ce so os el eu bse 6 oblate eee 116 
Leaded zinc oxide (see Zine oxide): 
Five per cent leaded... ... ...72.)ye setae eee 94 
Thirty-five per cent leaded.................. 95 
Lead-free zinc oxide (see Zinc oxide). ..........2.eeee eer eceees O34: 
br rYs Wey <0 |: EC eM 62 
Sulphate (PbSO,—total Pb-O as), test for............ 115, 116 
LeClair: . sole cco as 0 o's oe Saye daldbie due slyle kee ent ener | Rake; 
Linseed oil, mixing with... ... 5. <5 .< ideo. cee oe 126, 135 
M 
Metals, total heavy, test for... 0%. 05s 0+ osu pene 118 
Mineral oil, test for... 4.20 eas de naw os aie eee 128, 136 
Moisture in zinc oxide, at 110°-C., test for. .....2.... sm eee 113 
Moisture, other volatile matter, test for.................- 126, 135 
O 
Oi absorption, test of 5.0... 0.4.26 «. s1 ole «se 104, 106 
Opacity (see Hiding power) ............. 0. sane 100, 103 
Ores, blendes ... 6 6 60 caus cane nse 2 oe une tenee 10 
Geography of Africa... ....6...... 7.1.) 9 14, 16 
Australia... vis ss sod + dete « Senne ee 14 
Austria... cog seh tote 5 se ee 16 
Belgium... 5.2. +... ss «> she eea 16 
Bulgaria... 24 does c5 5 + ot 2 16 
Canada... .. 0... euscle ss 2a pee 14 
China... 5. suses see) po 17 
France . .coj50 bc ee lk fe > 0m 0c 16 
Germany. .... 6... 0 17 
Greece... 6.6 5s cin oe 6 4 oe A 17 
India. . 9.0.2. aus 05 nt 16 
Ttaly . . 0 .és..000 os Gia ele ae 17. 


INDEX 143 


PAGE 

ert Ve NOLIWAY as... ben peed ccc ee eles OMe dS 17 

PRMScO MRS Ma Cue et ard aay PhS ou eR 17 

COE Sele goes penn Mee oP a a ra 17 

LEGS ST ae SU Ale ae eat eee, Ane nt a ok a a 14 

nited OAc ).0 0. es Oe SS 18, 23 

OM hat. olny okcierde ne ide week bbws PEER ELA EL, 10 

am Me ys Baca raves ck accik pays tla Sn be de ha Oe e ed's 10 

eI hee Ce div hie Biel a wR le ee EDS oh ec 9 

Re Oe LUN ge clyvalcas ieee ee ee pale hee de ie ts 12 

EF 

ete sk pln gy cle Sad we hava w een se ees 73, 74 

i Gh yoke die Biv Sato Gen ol ticiw ek eh 4 wae a a 3 

Dr tretes Conree aNd SKINS ) 22. ce a eee eee eee 125, 129 

Per iclewmise OF ZINC OXIdE.. 6. ha ee ee Pee sa deary eee ah 25 

; NERC ME EA I ee eee ls se Sie eee eS 111 

PICS ING ORIN jie letsirine Scan wan suey eet Oa ewes 46 

Pemical constituents. to.) Pere Tee ee ela 89 

Pe ee ecto ea Ge sy bab duis wind 5 Pos B he ee oe 3 8s 47 

ay ea PTO DeLileS As ccs) Oarca es Wk Me ee ee ans 89 

: RE MR ee Fete iw Ge Sra eee al. 48 
Physical testing methods: 

PRTC AIS(OTIOG ee diaic caine 8 oh a dee pee eA WS aes 110 

Ree Ril es eg ele er haa Sa dade eee a ewe ee 98 

ai es ks wt d eles PE we SL ee Re gee he 97 

CoP PL el? SL i a a a 108 

MMR NEE eesti cid oi) day erslvra eee eye Mie x Soe 100, 103 

Re ee cry ed os o Seh as ea wo aS Ss Se eee 104, 106 

ME PEAR hy yt. ia wie vince a cateks @ BEA OEE Oa a Ss aly 111 

MG ee cS ack uc 4 ie EMORY ee Ga ee ae 110 

Be MPL err ele. ec ke voles pea eee wes baa 101 

smoothness, freedom from specks. ............22.0000 0000 99 

MO i ng screw, o's 6 4 oho Sha WU wee ANS cre MEL ie 102 

Peusmemrrengcih, ClONGALION. .... sé. ec div cou ot ase ee ene da ote 109 

Pe OSAMA LION OF waciii lave ote eons -aceeaGieny eyes oe ale made 127, 135 

Pe erecTiPearO 10), DASUG ce” iv 2 «sess eeee 6b w xd cag ee 127, 1385 

PPM eR ITE FOITORVAINCG™ cos tyes cave soe ve soe a telele ok bie o's wee ee 131, 136 

Re RIM TOCICIO SOLUUIOTIN Som oui ce vee oka bm ele d ace woes ote ly i137 

: R 
eM ESTE IGT Cty ova de meet otimre ee or RE ae 2d och ema RMT eT eRe 54 


Ee Ty ty nid As GA's « mena oe oe < oe Rs Ae DE ee ne rey £00 


144 INDEX 


Red seal zine Oxide. 2... 6g scepe pce eceves ob eres 00:9. my Hen nr 45 
Retorts, spelter os... 5..2c% 5 set bo ope tees ce one 31 
Cleaning: of...) 1.6/0.5)... <:g9- or 34 
Zine Onda a eee OP a 40 

Rubber makers’ lead-free zinc oxide: 
Chemical constituents. .........°).. +-4\:c)« selene 91 
Physical properties .............:0s «diss hus Oe 91 

Rubber makers’ superfine zine oxide: 
Chemical constituents... ..-..... « «« <s essa leaner eene sen 92 
Physical properties... 0.4.0. 010 op oe 2 Cert Cr: 
S 

Sampling method, zinc oxide... ...4...s0se ane eee 96 
OVeS. oc ep ens bp eens se edias se Bee 52 
Sampling, U.S. Government method. ©). ji:), a eee 123 
Settling in water, test Of, ,.......%4+. 5. wie eee anne 101 
Scoop for sampling. . ... 2.4. 2% ss a.000s oe 96 
Silver in Zinc OTES.... py ese co a yo ee de 0d 0) 23 
SKINS: 6.5 eae ees bin es wee eg os oe veep 129, 136 
SKIP Cars. eee. loeb bea an payee cs © ale ie leon 53 
‘Slab zinc, manufacture of (see Spelter)..............s.)0us eas eee 
Salts, soluble in water....¢.,....+.% «00 «05 een 134 
Smithsonite Zine OTE: 2... cys eee bees a wo es 13 
Smoothness, freedom from specks, test of... 5.72 4..0e se eee 99 
Sodium hydroxide (aqueous), . .........-..... eee 130, 137 
(Alcoholic)... :.)se.+7+ 02) 1346 137 
Sodium thiosulphate solution... +... ...i.2 95 130, 136 
Soluble salts, in water, test for... ...c...1..6.. «2 eee 112 
Specks, freedom from—smoothness:..... ....). /. ee 99 
Spelter furnace, charge..........4..544.4- 5< «0 er 33 
Spelter, manufacture of... ... 1.1.04 4.04 0a). Se 27 
Use of... baw ee cee aoe ei nle den en 37 
Starch solution, «0.010406. cn an womens ele See 130, 136 
Sulphide zine ores. .2..5:).+:+0210s3 05 vs 00 one 10 
Sulphur (as SO;3), test for.......0.....50p «0h 114, 120 
Dioxide, test for... 5.6 60.4 efi 1 2 119 
Government test for:........:....) 0) ee 125 
In charge... ccc nk ew can bee ee 61, 62 


ID OF OS en kn ea wn ow ee ee PBA Gh a | 


INDEX 145 


PAGE 
a 

RNa ify Fes eee kv hae lea ce Ges tv Cea wes 102 

Tensile strength and elongation, test of................ 000 cease 109 

ean Me eT Doan cave ele ss pda dp'elbe eee deve 79 

Pra Veumererave 1UINAce, ZINC OXIdE..,..6... 00.6 .6e ccc e env ececs 75 
U 

Peo wiea eto Or wine titrations...) ..46o. 0d eee ee. 1317136 
V 

ee a die scr Gk he ch se tee ebb n eee 3 

Pe oe A A laa aan 58, 78 
W 

RING KIO el, ws eis ees vied vp 00 occ AN Rear re hie 

Western practice, American process zinc oxide........./.....44 80 

Oe BS Ngo Ok Coan ihe belt eo 2 84 

REE AE th ip est) a die ited as ce dia ene ewe ges « 7 

Ee A ec nd teks einai + eno Wis Seige ews 80, 85 

iy gf os Fo i aks se ob se ope esos 5 

MESO Gy rice kn cc ce at lee atlines sere ndnetas 45 

ee ges ew uy te pls nah yen een ew laces 12 

C2 GS Rat Sets Mee 9 ice e 10 
Z 

ee ys vlc vn dee ne ee aN me ee ode ees 37 

ea os Oh hes sla a's civ d oia's ares iv ele due e'a 12 

Zinc oxide, American process: 

: PEA RLEEN DT UCUCE . 1 Lo aca nt Pa eC 59 

VP OCU ae ay 6) 4 La Uc aera Ute BaP Ene NOt re sl 

Ree eTIO eT ICAOCU. 20 acts edie tile « vx o's ohm ais wk 49 

Maoniea | COnstittients.; tau) s< i § Pokal 94 

eRe asiOrl DTODET HES ein ane [s bred Moe ea 94 

COSTE TOTS 1a SP aR 8 VE Rr OO 

Bree CPS UAOT iene sis. 5 os x ee os cpt orator TERE ces 61 

Lead free, chemical constituents ................0005 93 

PAV sical <DIODerbicd mam... . .. vr duke a sels s 93 

Se ATCO oe ee 0k EMI one, bed Seenas SP ae ERS 24 

RUMOR Steed si. 3 FN is cee ht a ae tke pur Mi Sica ate os 117 

Test for, U.S. Government: method. 2. .005...0. 0455 134 


Thirty-tive per cent leaded, chemical constituents.... 95 
Physical properties...... 95 





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